Paracellular permeation-enhancing effect of AT1002 C-terminal amidation in nasal delivery.

BACKGROUND: The identification of permeation enhancers has gained interest in the development of drug delivery systems. A six-mer peptide, H-FCIGRL-OH (AT1002), is a tight junction modulator with promising permeation-enhancing activity. AT1002 enhances the transport of molecular weight markers or agents with low bioavailability with no cytotoxicity. However, AT1002 is not stable in neutral pH or after incubation under physiological conditions, which is necessary to fully uncover its permeation-enhancing effect. Thus, we increased the stability or mitigated the instability of AT1002 by modifying its terminal amino acids and evaluated its subsequent biological activity. METHODS: C-terminal-amidated (FCIGRL-NH2, Pep1) and N-terminal-acetylated (Ac-FCIGRL, Pep2) peptides were analyzed by liquid chromatography-mass spectrometry. We further assessed cytotoxicity on cell monolayers, as well as the permeation-enhancing activity following nasal administration of the paracellular marker mannitol. RESULTS: Pep1 was nontoxic to cell monolayers and showed a relatively low decrease in peak area compared to AT1002. In addition, administration of mannitol with Pep1 resulted in significant increases in the area under the plasma concentration-time curve and peak plasma concentration at 3.63-fold and 2.68-fold, respectively, compared to mannitol alone. In contrast, no increase in mannitol concentration was shown with mannitol/AT1002 or mannitol/Pep2 compared to the control. Thus, Pep1 increased the stability or possibly reduced the instability of AT1002, which resulted in an increased permeation-enhancing effect of AT1002. CONCLUSION: These results suggest the potential usefulness of C-terminal-amidated AT1002 in enhancing nasal drug delivery, which may lead to the development of a practical drug delivery technology for drugs with low bioavailability.

A Methanol Extract of Adansonia digitata L. Leaves Inhibits Pro-Inflammatory iNOS Possibly via the Inhibition of NF-κB Activation.

This study examined the total polyphenol content of eight wild edible plants from Ethiopia and their effect on NO production in Raw264.7 cells. Owing to its relatively high polyphenol concentration and inhibition of NO production, the methanol extract of Adansonia digitata L. leaf (MEAD) was subjected to detailed evaluation of its antioxidant and anti-inflammatory effects. Antioxidant effects were assessed by measuring free-radical-scavenging activity using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and oxygen-radical-absorbance capacity (ORAC) assays, while anti-inflammatory effects were assessed by measuring inducible nitric oxide synthase (iNOS) expression in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. In the ORAC assay, MEAD was 10.2 times more potent than vitamin C at eliminating peroxyl radicals. In DPPH assay, MEAD also showed a strong ROS scavenging effect. MEAD significantly inhibited iNOS activity (IC50=28.6 µg/ml) of LPS-stimulated Raw264.7 cells. We also investigated the relationship between iNOS expression and nuclear factor kappa B (NF-κB) activation. MEAD inhibited IκBα degradation and NF-κB translocation from the cytosol to the nucleus in LPS-induced RAW264.7 cells without significant cytotoxic effects, as confirmed by MTT assay. These results suggest that MEAD inhibits anti-inflammatory iNOS expression, which might be related to the elimination of peroxyl radicals and thus the inhibition of IκBα-mediated NF-κB signal transduction.

Tert-butylhydroquinone reduces lipid accumulation in C57BL/6 mice with lower body weight gain.

tert-Butylhydroquinone (tBHQ) is a commonly used antioxidant additive that is approved for human use by both the Food and Agriculture Organization and the World Health Organization (FAO/WHO). In this study, we examined the effect of tBHQ on body weight gain and found that food supplementation with 0.001 % (w/w) tBHQ inhibited 61.4 % (P < 0.01) of body weight gain in high-fat diet (HFD)-induced C57BL/6 mice, and the oral administration of tBHQ (1.5 mg/kg) reduced 47.5 % (P < 0.05) of body weight gain in normal diet fed db/db mice. The HFD increased lipid deposit in adipocytes, but these were reduced significantly by tBHQ treatment in C57BL/6 mice. tBHQ supplementation significantly lowered the plasma triglyceride and total cholesterol, with reduced size of accumulated fat mass. The rate limiting enzyme of beta-oxidation (ACOX1) was significantly over-expressed in the liver with tBHQ treatment. These results indicate that tBHQ suppresses body weight gain in mice, possibly at least related to the up-regulation of ACOX1 gene expression.

Characterization of alcohol dehydrogenase 3 of the thermotolerant methylotrophic yeast Hansenula polymorpha.

In this study, we identified and characterized mitochondrial alcohol dehydrogenase 3 from the thermotolerant methylotrophic yeast Hansenula polymorpha (HpADH3). The amino acid sequence of HpADH3 shares over 70% of its identity with the alcohol dehydrogenases of other yeasts and exhibits the highest similarity of 91% with the alcohol dehydrogenase 1 of H. polymorpha. However, unlike the cytosolic HpADH1, HpADH3 appears to be a mitochondrial enzyme, as a mitochondrial targeting extension exists at its N terminus. The recombinant HpADH3 overexpressed in Escherichia coli showed similar catalytic efficiencies for ethanol oxidation and acetaldehyde reduction. The HpADH3 displayed substrate specificities with clear preferences for medium chain length primary alcohols and acetaldehyde for an oxidation reaction and a reduction reaction, respectively. Although the H. polymorpha ADH3 gene was induced by ethanol in the culture medium, both an ADH isozyme pattern analysis and an ADH activity assay indicated that HpADH3 is not the major ADH in H. polymorpha DL-1. Moreover, HpADH3 deletion did not affect the cell growth on different carbon sources. However, when the HpADH3 mutant was complemented by an HpADH3 expression cassette fused to a strong constitutive promoter, the resulting strain produced a significantly increased amount of ethanol compared to the wild-type strain in a glucose medium. In contrast, in a xylose medium, the ethanol production was dramatically reduced in an HpADH3 overproduction strain compared to that in the wild-type strain. Taken together, our results suggest that the expression of HpADH3 would be an ideal engineering target to develop H. polymorpha as a substrate specific bioethanol production strain.

Identification of the genes involved in 1-deoxynojirimycin synthesis in Bacillus subtilis MORI 3K-85.

1-Deoxynojirimycin (DNJ), a D-glucose analogue with a nitrogen atom substituting for the ring oxygen, is a strong inhibitor of intestinal α-glucosidase. DNJ has several promising biological activities, including its antidiabetic, antitumor, and antiviral activities. Nevertheless, only limited amounts of DNJ are available because it can only be extracted from some higher plants, including the mulberry tree, or purified from the culture broth of several types of soil bacteria, such as Streptomyces sp. and Bacillus sp. In our previous study, a DNJ-producing bacterium, Bacillus subtilis MORI, was isolated from the traditional Korean fermented food Chungkookjang. In the present study, we report the identification of the DNJ biosynthetic genes in B. subtilis MORI 3K-85 strain, a DNJ-overproducing derivate of the B. subtilis MORI strain generated by γ-irradiation, xhe genomic DNA library of B. subtilis MORI 3K-85 was constructed in Escherichia coli, and clones showing α-glucosidase inhibition activity were selected. After DNA sequencing and a series of subcloning, we were able to identify a putative Operon which consists of gabT1, yktc1, and gutB1 genes predicted to encode putative transaminase, phosphatase, and oxidoreductase, respectively. When a recombinant plasmid containing this Operon sequence was transformed into an E. coli strain, the resulting transformant was able to produce DNJ into the culture medium. Our results indicate that the gabT1, yktc1, and gutB1 genes are involved in the DNJ biosynthetic pathway in B. subtilis MORI, suggesting the possibility of employing these genes to establish a large-scale microbial DNJ overproduction system through genetic engineering and process optimization.

Evidences for correlation between the reduced VCAM-1 expression and hyaluronan synthesis during cellular senescence of human mesenchymal stem cells.

Mesenchymal stem cells (MSCs) undergo cellular senescence during in vitro expansion culture, which accompanies the loss of migration and homing abilities. In this study, we analyzed expression levels of several surface markers of human MSCs at different passages of expansion culture. It has been shown that expression of vascular cell adhesion molecule-1 (VCAM-1) was most markedly decreased among the tested markers in the senescent MSCs. Interestingly the reduced VCAM-1 expression could be restored by applying hyaluronan, a major glycosaminoglycan ligand of CD44, to the culture. It was found that the hyaluronan level in extracellular and pericellular matrices was greatly reduced in the senescent MSCs, mainly due to the decreased expression of hyaluronan synthases, suggesting a correlation between the reduced VCAM-1 expression and hyaluronan synthesis. In fact, when hyaluronan synthases were knock-downed by siRNA transfection, the VCAM-1 expression was also reduced. Our results indicate that VCAM-1 expression in the senescent MSCs was down-regulated because of the reduced synthesis of hyaluronan. Thus, we suggest that hyaluronan supplementation in expansion culture of MSCs would compensate adverse effects induced by its decreased synthesis and subsequently enhance cell adhesion and migration abilities.

Enhanced production of human serum albumin by fed-batch culture of Hansenula polymorpha with high-purity oxygen.

Fed-batch cultures of Hansenula polymorpha were studied to develop an efficient biosystem to produce recombinant human serum albumin (HSA). To comply with this purpose, we used high purity oxygen supplying strategy to increase viable cell density in a bioreactor and enhance the production of target protein. A mutant strain, H. polymorpha GOT7 was utilized in this study as a host strain in both 5-L and 30-L scale fermentors. To supply high purity oxygen into a bioreactor, nearly 100 % high purity oxygen from commercial bomb or higher than 93 % oxygen available in-situ from a pressure swing adsorption oxygen generator (PSA) was employed. Under the optimal fermentation of H. polymorpha with high purity oxygen, the final cell densities and produced HSA concentrations were 24.6 g/L and 5.1 g/L in the 5-L fermentor, and 24.8 g/L and 4.5 g/L in the 30-L fermentor, respectively. These were about 2-10 times higher than those obtained in air-based fed-batch fermentations. The discrepancies between the 5-L and 30-L fermentors with air supply were presumably due to the higher contribution of surface aeration over submerged aeration in the 5-L fermentor. This study, therefore, proved the positive effect of high purity oxygen to enhance viable cell density as well as target recombinant protein production in microbial fermentations.

Multiple-yapsin-deficient mutant strains for high-level production of intact recombinant proteins in Saccharomyces cerevisiae.

The yapsin family of aspartic proteases, located at cell surface, has a common specificity for paired or single basic reside cleavage sites of proproteins. Our previous study reported that the aberrant proteolytic cleavage of secretory recombinant human parathyroid hormone (hPTH) protein was problematic at late stages of fed-batch cultivations, even in the Saccharomyces cerevisiae mutant strain deficient in yapsin 1 (yps1Delta). To overcome this problem, we constructed a set of S. cerevisiae mutant strains lacking several members of the yapsin family through disruption of the YPS genes coding for yapsin 1, 2, 3, 6, and 7 proteases in various combinations. The multiple YPS-deletion mutant strains did not show detectable growth defects under normal growth conditions, although some of them were hypersensitive to hygromycin B, acid (pH 3.5) and alkali (pH 8.0) conditions. The quintuple disruptant (yps1Deltayps2Deltayps3Deltayps6Deltayps7Delta) was the most efficient in preventing the proteolytic degradation of hPTH in fed-batch cultivations. The present data strongly indicate the involvement of other yapsin members besides Yps1p in the proteolysis of secretory recombinant proteins, particularly under high-density growth conditions.

Characterization of alcohol dehydrogenase 1 of the thermotolerant methylotrophic yeast Hansenula polymorpha.

The thermotolerant methylotrophic yeast Hansenula polymorpha has recently been gaining interest as a promising host for bioethanol production due to its ability to ferment xylose, glucose, and cellobiose at elevated temperatures up to 48 degrees C. In this study, we identified and characterized alcohol dehydrogenase 1 of H. polymorpha (HpADH1). HpADH1 seems to be a cytoplasmic protein since no N-terminal mitochondrial targeting extension was detected. Compared to the ADHs of other yeasts, recombinant HpADH1 overexpressed in Escherichia coli exhibited much higher catalytic efficiency for ethanol oxidation along with similar levels of acetaldehyde reduction. HpADH1 showed broad substrate specificity for alcohol oxidation but had an apparent preference for medium chain length alcohols. Both ADH isozyme pattern analysis and ADH activity assay indicated that ADH1 is the major ADH in H. polymorpha DL-1. Moreover, an HpADH1-deleted mutant strain produced less ethanol in glucose or glycerol media compared to wild-type. Interestingly, when the ADH1 mutant was complemented with an HpADH1 expression cassette, the resulting strain produced significantly increased amounts of ethanol compared to wild-type, up to 36.7 g l(-1). Taken together, our results suggest that optimization of ADH1 expression would be an ideal method for developing H. polymorpha into an efficient bioethanol production strain.

Gene cloning, characterization, and heterologous expression of levansucrase from Bacillus amyloliquefaciens.

Although levan produced by Bacillus amyloliquefaciens is known to have efficient immunostimulant property which gives 100% survival of common carp when infected with Aeromonas hydrophila, no detailed reports are available describing kinetic studies of D: -glucose production and levan formation. In this study, we cloned and characterized the enzymatic kinetics using levansucrase expressed in Escherichia coli. Optimum pH for D: -glucose production and levan formation was 6.0 and 8.0, respectively, whereas optimum temperature was 30 degrees C and 4 degrees C, respectively. The K (m) and V (max) values for levansucrase were calculated to be 47.81 mM sucrose and 57.47 1mole/min mg protein, respectively. Prominent expression of levansucrase was obtained through xylose induction in Bacillus megaterium, where most of the His(6)-tagged protein was secreted into the culture broth, giving levansucrase activity of 12,906 U/l. Response-surface methodology (RSM) was further employed to optimize the fermentation conditions and improve the level of levansucrase production. Maximum levansucrase activity of 20,251 U/l was obtained in 12 h of fermentation carried out at 28 degrees C, starting induction with 0.735% xylose when A (600) was 1.2, which was 1.6- and 62-fold higher than those obtained in the nonoptimized conditions for the recombinant strain and the native strain, respectively.

An efficient plasmid vector for constitutive high-level expression of foreign genes in Escherichia coli.

The levansucrase gene (lsrA) from Rahnella aquatilis was strongly expressed in a constitutive manner in Escherichia coli when cloned into a pBluescript KS-based pRL1CP plasmid vector. The native promoter upstream of lsrA and the lacZ promoter cooperatively enhanced the expression of lsrA to a level that was comparable to that of the T7 promoter, which is used in commercial pET expression vector system. A putative rho-independent transcription termination signal downstream of lsrA was crucial for gene expression. This plasmid vector also proved to be applicable for efficient expression of other foreign genes in E. coli.

Glycoengineering of the methylotrophic yeast Hansenula polymorpha for the production of glycoproteins with trimannosyl core N-glycan by blocking core oligosaccharide assembly.

The initial lipid-linked oligosaccharide Glc(3)Man(9)GlcNAc(2)-dolichyl pyrophosphate (Dol-PP) for N-glycan is synthesized and assembled at the membrane of the endoplasmic reticulum (ER) and subsequently transferred to a nascent polypeptide by the oligosaccharide transferase complex. We have identified an ALG3 homolog (HpALG3) coding for a dolichyl-phosphate-mannose dependent alpha-1,3-mannosyltransferase in the methylotrophic yeast Hansenula polymorpha. The detailed analysis of glycan structure by linkage-specific mannosidase digestion showed that HpALG3 is responsible for the conversion of Man5GlcNAc(2)-Dol-PP to Man(6)GlcNAc(2)-Dol-PP, the first step to attach a mannose to the lipid-linked oligosaccharide in the ER. The N-glycosylation pathway of H. polymorpha has been remodeled by deleting the HpALG3 gene in the Hpoch1 null mutant strain blocked in the yeast-specific outer mannose chain synthesis and by introducing an ER-targeted Aspergillus saitoi alpha-1,2-mannosidase gene. This glycoengineered H. polymorpha strain produced glycoproteins mainly containing trimannosyl core N-glycan (Man(3)GlcNAc(2)), which is the common core backbone of various human-type N-glycans. The results demonstrate the high potential of H. polymorpha to be developed as an efficient expression system for the production of glycoproteins with humanized glycans.

Identification of the cadmium-inducible Hansenula polymorpha SEO1 gene promoter by transcriptome analysis and its application to whole-cell heavy-metal detection systems.

The genomewide gene expression profiling of the methylotrophic yeast Hansenula polymorpha exposed to cadmium (Cd) allowed us to identify novel genes responsive to Cd treatment. To select genes whose promoters can be useful for construction of a cellular Cd biosensor, we further analyzed a set of H. polymorpha genes that exhibited >6-fold induction upon treatment with 300 muM Cd for 2 h. The putative promoters, about 1,000-bp upstream fragments, of these genes were fused with the yeast-enhanced green fluorescence protein (GFP) gene. The resultant reporter cassettes were introduced into H. polymorpha to evaluate promoter strength and specificity. The promoter derived from the H. polymorpha SEO1 gene (HpSEO1) was shown to drive most strongly the expression of GFP upon Cd treatment among the tested promoters. The Cd-inducible activity was retained in the 500-bp deletion fragment of the HpSEO1 promoter but was abolished in the further truncated 250-bp fragment. The 500-bp HpSEO1 promoter directed specific expression of GFP upon exposure to Cd in a dose-dependent manner, with Cd detection ranging from 1 to 900 muM. Comparative analysis of the Saccharomyces cerevisiae SEO1 (ScSEO1) promoter revealed that the ScSEO1 promoter has a broader specificity for heavy metals and is responsive to arsenic and mercury in addition to Cd. Our data demonstrate the potential use of the HpSEO1 promoter as a bioelement in whole-cell biosensors to monitor heavy metal contamination, particularly Cd.

Cyclization mechanism of amorpha-4,11-diene synthase, a key enzyme in artemisinin biosynthesis.

Cyclization of farnesyl diphosphate into amorpha-4,11-diene by amorpha-4,11-diene synthase (ADS) initiates biosynthesis of artemisinin, a clinically important antimalarial drug precursor. Three possible ring-closure mechanisms, two involving a bisabolyl carbocation intermediate followed by either a 1,3-hydride shift or two successive 1,2-shifts, and one involving a germacrenyl carbocation, were proposed and tested by analyzing the fate of farnesyl diphosphate H-1 hydrogen atoms through (1)H and (2)H NMR spectroscopy. Migration of one deuterium atom of [1,1-(2)H(2)]farnesyl diphosphate to H-10 of amorpha-4,11-diene singled out the bisabolyl carbocation mechanism with a 1,3-hydride shift. Further confirmation was obtained through enzyme reactions with (1R)- and (1S)-[1-(2)H]farnesyl diphosphate. Results showed that deuterium of the 1R compound remained at H-6, whereas that of the 1S compound migrated to H-10 of amorpha-4,11-diene. Incorporation of one deuterium into amorphadiene in the cyclization process was observed when the reaction was performed in (2)H(2)O, as evidenced by an increase of 1 amu in the mass of the molecular ion.

Functional characterization of the Hansenula polymorpha HOC1, OCH1, and OCR1 genes as members of the yeast OCH1 mannosyltransferase family involved in protein glycosylation.

The alpha-1,6-mannosyltransferase encoded by Saccharomyces cerevisiae OCH1 (ScOCH1) is responsible for the outer chain initiation of N-linked oligosaccharides. To identify the genes involved in the first step of outer chain biosynthesis in the methylotrophic yeast Hansenula polymorpha, we undertook the functional analysis of three H. polymorpha genes, HpHOC1, HpOCH1, and HpOCR1, that belong to the OCH1 family containing seven members with significant sequence identities to ScOCH1. The deletions of these H. polymorpha genes individually resulted in several phenotypes suggestive of cell wall defects. Whereas the deletion of HpHOC1 (Hphoc1Delta) did not generate any detectable changes in N-glycosylation, the null mutant strains of HpOCH1 (Hpoch1Delta) and HpOCR1 (Hpocr1Delta) displayed a remarkable reduction in hypermannosylation. Although the apparent phenotypes of Hpocr1Delta were most similar to those of S. cerevisiae och1 mutants, the detailed structural analysis of N-glycans revealed that the major defect of Hpocr1Delta is not in the initiation step but rather in the subsequent step of outer chain elongation by alpha-1,2-mannose addition. Most interestingly, Hpocr1Delta showed a severe defect in the O-linked glycosylation of extracellular chitinase, representing HpOCR1 as a novel member of the OCH1 family implicated in both N- and O-linked glycosylation. In contrast, addition of the first alpha-1,6-mannose residue onto the core oligosaccharide Man8GlcNAc2 was completely blocked in Hpoch1Delta despite the comparable growth of its wild type under normal growth conditions. The complementation of the S. cerevisiae och1 null mutation by the expression of HpOCH1 and the lack of in vitro alpha-1,6-mannosyltransferase activity in Hpoch1Delta provided supportive evidence that HpOCH1 is the functional orthologue of ScOCH1. The engineered Hpoch1Delta strain with the targeted expression of Aspergillus saitoi alpha-1,2-mannosidase in the endoplasmic reticulum was shown to produce human-compatible high mannose-type Man5GlcNAc2 oligosaccharide as a major N-glycan.

Characteristics of Saccharomyces cerevisiae gal1 Delta and gal1 Delta hxk2 Delta mutants expressing recombinant proteins from the GAL promoter.

Galactose can be used not only as an inducer of the GAL promoters, but also as a carbon source by Saccharomyces cerevisiae, which makes recombinant fermentation processes that use GAL promoters complicated and expensive. To overcome this problem during the cultivation of the recombinant strain expressing human serum albumin (HSA) from the GAL10 promoter, a gal1 Delta mutant strain was constructed and its induction kinetics investigated. As expected, the gal1 Delta strain did not use galactose, and showed high levels of HSA expression, even at extremely low galactose concentrations (0.05-0.1 g/L). However, the gal1 Delta strain produced much more ethanol, in a complex medium containing glucose, than the GAL1 strain. To improve the physiological properties of the gal1 Delta mutant strain as a host for heterologous protein production, a null mutation of either MIG1 or HXK2 was introduced into the gal1 Delta mutant strain, generating gal1 Delta mig1 Delta and gal1 Delta hxk2 Delta double strains. The gal1 Delta hxk2 Delta strain showed a decreased rate of ethanol synthesis, with an accelerated rate of ethanol consumption, compared to the gal1 Delta strain, whereas the gal1 Delta mig1 Delta strain showed similar patterns to the gal1 Delta strain. Furthermore, the gal1 Delta hxk2 Delta strain secreted much more recombinant proteins (HSA and HSA fusion proteins) than the other strains. The results suggest that the gal1 Delta hxk2 Delta strain would be useful for the large-scale production of heterologous proteins from the GAL10 promoter in S. cerevisiae.

Cloning and characterization of the Hansenula polymorpha PEP4 gene encoding proteinase A.

The Hansenula polymorpha PEP4 gene encoding proteinase A was cloned by Southern blot hybridization using the Saccharomyces cerevisiae PEP4 gene as probe and characterized by gene disruption and overexpression. Nucleotide sequence analysis revealed an open reading frame (ORF) of 1239 nucleotides corresponding to a polypeptide of 413 amino acids, sharing about 67.2% sequence similarity with that of S. cerevisiae proteinase A. That the cloned H. polymorpha PEP4 gene encodes proteinase A was supported by a gene disruption experiment, which showed that the H. polymorpha pep4 mutant strain showed significantly reduced level of carboxypeptidase Y activity when assayed with an artificial substrate. When the PEP4 gene is overproduced in pep4 mutant strain, mature proteinase A could be found in the growth medium. N-terminal amino acid sequencing of extracellular proteinase A revealed the presence of a putative propeptide of 55 amino acids ending with a dibasic peptide (Lys-Arg), probably processed by Kex2p-like endopeptidase of H. polymorpha. The nucleotide sequence of the H. polymorpha PEP4 gene has been submitted to GenBank under Accession No. U67173.

Characterization of N-linked oligosaccharides assembled on secretory recombinant glucose oxidase and cell wall mannoproteins from the methylotrophic yeast Hansenula polymorpha.

Presently almost no information is available on the oligosaccharide structure of the glycoproteins secreted from the methylotrophic yeast Hansenula polymorpha, a promising host for the production of recombinant proteins. In this study, we analyze the size distribution and structure of N-linked oligosaccharides attached to the recombinant glycoprotein glucose oxidase (GOD) and the cell wall mannoproteins obtained from H. polymorpha. Oligosaccharide profiling showed that the major oligosaccharide species derived from the H. polymorpha-secreted recombinant GOD (rGOD) had core-type structures (Man(8-12)GlcNAc(2)). Analyses using anti-alpha 1,3-mannose antibody and exoglycosidases specific for alpha 1,2- or alpha 1,6-mannose linkages revealed that the mannose outer chains of N-glycans on the rGOD have very short alpha 1,6 extensions and are mainly elongated in alpha 1,2-linkages without a terminal alpha 1,3-linked mannose addition. The N-glycans released from the H. polymorpha mannoproteins were shown to contain mostly mannose in their outer chains, which displayed almost identical size distribution and structure to those of H. polymorpha-derived rGOD. These results strongly indicate that the outer chain processing of N-glycans by H. polymorpha significantly differs from that by Saccharomyces cerevisiae, thus generating much shorter mannose outer chains devoid of terminal alpha 1,3-linked mannoses.

Properties of the Hansenula polymorpha-derived constitutive GAP promoter, assessed using an HSA reporter gene.

The glyceraldehyde-3-phosphate dehydrogenase promoter, P(GAP), was employed to direct the constitutive expression of recombinant human serum albumin (HSA) in Hansenula polymorpha. A set of integration vectors containing the HSA cDNA under the control of P(GAP) was constructed and the elemental parameters affecting the expression of HSA from P(GAP) were analyzed. The presence of a 5'-untranslated region derived from the HSA cDNA and the integration of the expression vector into the GAP locus were shown to improve the expression of HSA under P(GAP). Glycerol supported a higher level of HSA expression from P(GAP) along with a higher cell density than either glucose or methanol. The growth at high glycerol concentrations up to 12% did not cause any significant repression of the cell growth. A high cell density culture, up to 83 g l(-1) dry cell weight with a HSA production of 550 mg l(-1), was obtained in less than 32 h of cultivation in a fed-batch fermentation employing intermittent feeding with 12% glycerol. The GAP promoter-based HSA expression system showed a higher specific production rate and required a much simpler fermentation process than the MOX promoter-based system, demonstrating that P(GAP) can be a practical alternative of the MOX promoter in the large-scale production of HSA from H. polymorpha.

Levan fructotransferase from Arthrobacter oxydans J17-21 catalyzes the formation of the di-D-fructose dianhydride IV from levan.

A new levan fructotransferase (LFTase) isolated from Arthrobacter oxydans J17-21 was characterized for the production of difructose dianhydride IV (DFA IV). LFTase was purified to apparent homogeneity by Q-Sepharose ion exchange chromatography, Mono-Q HR 5/5 column chromatography, and gel permeation chromatography. The enzyme had an apparent molecular mass of 54000 Da. The optimum pH for the enzyme-catalyzed reaction was pH 6.5, and the optimum temperature was observed at 45 degrees C. The LFTase was activated by the presence of CaCl(2) and EDTA-2Na but inhibited strongly by MnCl(2) and CuSO(4) at 1 mM and completely by FeSO(4) and Ag(2)SO(4) at 1 mM. A bacterial levan from Zymomonas mobilis was incubated with an LFTase; final conversion yield from the levan to DFA IV was 35%. Neither inulin, levanbiose, sucrose, dextran, nor starch was hydrolyzed by LFTase. DFA IV was very stable at acidic pH and high temperature, thus indicating that DFA IV may be suitable for the food industry and related areas.