Efficient production of transgenic melon via Agrobacterium-mediated transformation.

Oriental melon (Cucumis melo L. var. makuwa) is an important fruit for human consumption. However, this plant species is one of the most recalcitrant to genetic transformation. The lack of an efficient in vitro system limits the development of a reproducible genetic transformation protocol for Oriental melon. In this study, an efficient transgenic production method for Agrobacterium-mediated transformation using cotyledon explants of Oriental melon was developed. Cotyledon explants were pre-cultivated for two days in the dark, and the optimal conditions for transformation of melon were determined to be a bacteria concentration of OD600 0.6, inoculation for 30 min, and two days of co-cultivation. Transgenic melon plants were produced from kanamycin-resistant shoots. A total of 11 independent transgenic plants were regenerated with a transformation efficiency of 0.8% of the inoculated explants. The transgenic plants were phenotypically normal and fully fertile, which might be a consequence of the co-cultivation time.

Characterization and heterologous expression of a novel lysophospholipase gene from Antrodia cinnamomea.

AIMS: A novel lysophospholipase (LysoPL) from the basidiomycetous fungi Antrodia cinnamomea named ACLysoPL was cloned, heteroexpressed in Escherichia coli and characterized. METHODS AND RESULTS: The gene encoding ACLysoPL was obtained from expressed sequence tags from A. cinnamomea. The full length of this gene has a 945 -bp open reading frame encoding 314 amino acids with a molecular weight of 35.5 kDa. ACLysoPL contains a lipase consensus sequence (GXSXG) motif and a Ser-His-Asp catalytic triad. A putative peroxisomal targeting signal type 1 was found in the C-terminal. Heterologous expression of ACLysoPL in E. coli showed that the enzyme preferentially hydrolyses long-chain acyl esterases at pH 7 and 30 degrees C. ACLysoPL is a psychrophilic enzyme about 40% of whose maximum activity remained at 4 degrees C. The LysoPL activities with lysophospholipids as substrate were analysed by gas chromatography/mass spectrometry. CONCLUSION: We have identified and characterized a gene named ACLysoPL encoding a protein performing LysoPL and esterase activities. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first LysoPL of A. cinnamomea identified and characterized at the molecular level.

Studies of optimum conditions for covalent immobilization of Candida rugosa lipase on poly(gamma-glutamic acid) by RSM.

Poly(gamma-glutamic acid) (gamma-PGA) is a material of polymer. Immobilization of Candida rugosa lipase (Lipase AY-30) by covalent binding on gamma-PGA led to a markedly improved performance of the enzyme. Response surface methodology (RSM) and 3-level-3-factor fractional factorial design were employed to evaluate the effects of immobilization parameters, such as immobilization time (2-6h), immobilization temperature (0-26 degrees C), and enzyme/support ratio (0.1-0.5, w/w). Based on the analysis of ridge max, the optimum immobilization conditions were as follows: immobilization time 2.3h, immobilization temperature 13.3 degrees C, and enzyme/support ratio 0.41 (w/w); the highest lipase activity obtained was 1196 U/mg-protein.

A 5-year audit of haemodialysis access.

This is a review of our experience with vascular access procedures over a 5-year period at Derriford Hospital, Plymouth, UK. The aims of the study were to examine the outcome of vascular access procedures and factors influencing access survival. Between April 1995 and March 2000, 151 patients who underwent 221 vascular access procedures were studied. Of these, 136 had autogenous arteriovenous fistulae, whereas 85 had prosthetic AV grafts (41% in the thigh). The overall primary failure rate was 21% whereas the 1- and 5-year cumulative access survival rates were 60 and 41%, respectively. Thigh grafts have a mean survival of 36 months compared with 32 months for prosthetic upper limb and 43 months for autogenous fistulae. Age, diabetes and predialysis status did not significantly influence access survival. Thrombosis was responsible for access failure in 62 cases (28%). Avoiding subclavian vein canulation and performing vessel mapping prior to access placement should reduce the risk of access failure due to outflow obstruction.

Multiple mutagenesis of the Candida rugosa LIP1 gene and optimum production of recombinant LIP1 expressed in Pichia pastoris.

Candida rugosa lipase, a significant catalyst, had been widely employed to catalyze various chemical reactions such as non-specific, stereo-specific hydrolysis and esterification for industrial biocatalytic applications. Several isozymes encoded by the lip gene family, namely lip1 to lip7, possess distinct thermal stability and substrate specificity, among which the recombinant LIP1 showed a distinguished catalytic characterization. In this study, we utilized PCR to remove an unnecessary linker of pGAPZalphaC vector and used overlap extension PCR-based multiple site-directed mutagenesis to convert the 19 non-universal CTG-serine codons into universal TCT-serine codons and successfully express a highly active recombinant C. rugosa LIP1 in the Pichia expression system. Response surface methodology and 4-factor-5-level central composite rotatable design were adopted to evaluate the effects of growth parameters, such as temperature (21.6-38.4 degrees C), glucose concentration (0.3-3.7%), yeast extract (0.16-1.84%), and pH (5.3-8.7) on the lipolytic activity of LIP1 and biomass of P. pastoris. Based on ridge max analysis, the optimum LIP1 production conditions were temperature, 24.1 degrees C; glucose concentration, 2.6%; yeast extract, 1.4%; and pH 7.6. The predicted value of lipolytic activity was 246.9+/-39.7 U/ml, and the actual value was 253.3+/-18.8 U/ml. The lipolytic activity of the recombinant LIP1 resulting from the present work is twofold higher than that achieved by a methanol induction system.

Lipase-catalyzed synthesis of fatty acid diethanolamides.

Diethanolamides are nonionic emulsifiers widely used in industries such as cosmetics and as corrosion inhibitors. Candida antarctica lipase (Novozym 435) was used to catalyze the amidation of various fatty acids with diethanolamine. Contents of fatty acids, metal ions, and water affected the yields of diethanolamides. Hexanoic acid was the best substrate among all acyl donors. Yields of hexanoyl diethanolamide (HADEA), lauroyl diethanolamide (LADEA), and oleoyl diethanolamide (OADEA), obtained after 24 h of lipase-catalyzed reaction at 50 degrees C and 250 rpm with 90 mM fatty acid and 360 mM diethanolamine in acetonitrile, were 76.5, 49.5, and 12.1%, respectively. Addition of 1 mM metal salts increased the yields of HADEA and LADEA. Kinetic analysis showed that the yields of HADEA and LADEA in lipase-catalyzed reactions were largely associated with the rate of the forward reaction constant k(1). Anhydrous enzyme was found to be the best for the amidation reaction. Study on the enzyme operational stability showed that C. antarctica lipase retained 95 and 85% of the initial activity for the syntheses of HADEA and LADEA, respectively (even after repeated use for 10 days). The reaction runs smoothly without the use of hazardous reactants, and the developed method is useful for the industrial application.

Formation of protoberberine-type alkaloids by the tubers of somatic embryo-derived plants of Corydalis yanhusuo.

The effects of 0.5 - 5 mg/l abscisic acid [ABA], 0.5 - 10 mg/l (2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)pentan-3-ol [paclobutrazol] and 0.5 - 2 mg/l alpha-cyclopropyl-alpha-(4-methoxyphenyl)-5-pyrimidinemethanol [ancymidol], 0.5 - 5 mg/l gibberellic acid [GA(3)] and 15 - 100 mg/l polyethylene glycol [PEG] 4000 supplemented in half-strength Murashige and Skoog's (MS) medium on the production of the two major protoberberine-type alkaloids (D,L-tetrahydropalmatine and D-corydaline) by the tubers of somatic embryo-derived plants of Corydalis yanhusuo were examined. Somatic embryo derived plants were also maintained for 6 months on half-strength MS medium containing 0.1 mg/l GA(3) or 0.5 mg/l paclobutrazol. The alkaloid contents were determined by high performance liquid chromatography (HPLC). The analysis revealed that the contents of D,L-tetrahydropalmatine and D-corydaline in the tubers of somatic embryo-derived plants were higher than the marketed crude drug and varied with growth regulator/PEG-4000 treatment and the age of the plant.

Recombinant expression and characterization of the Candida rugosa lip4 lipase in Pichia pastoris: comparison of glycosylation, activity, and stability.

Although Candida rugosa utilizes a nonuniversal serine codon (CUG) for leucine, it is possible to express lipase genes (LIP) in heterologous systems. After replacing the 19 CUG codons in LIP4 with serine codons by site-directed mutagenesis, a recombinant LIP4 was functionally overexpressed in Pichia pastoris in this study. This recombinant glycosylated lipase was secreted into the culture medium with a high purity of 100 mg/liter in a culture broth. Purified recombinant LIP4 had a molecular mass of 60 kDa, showing a range similar to that of lipase in a commercial preparation. Since LIP4 has only a glycosylation site at position Asn-351, this position may also be the major glycosylation site in C. rugosa lipases. Although the thermal stability of recombinant LIP4 significantly increased from 52 to 58 degrees C after glycosylation, there were no significant differences in the catalytic properties of recombinant glycosylated lipase from P. pastoris and the unglycosylated one from Escherichia coil. These two recombinant LIP4s showed higher esterase activities toward long-chain ester (C16 and C18) and exhibited higher lipase activities toward unsaturated and long-chain lipids. In addition, LIP4 does not show interfacial activation as compared with LIP1 toward lipid substrates of tributyrin and triolein. These observations demonstrated that LIP4 shows distinguished catalytic activities with LIP1 in spite of their high sequence homology.

Synthesis of fatty acid esters by recombinant Staphylococcus epidermidis lipases in aqueous environment.

Various flavor esters were obtained by using recombinant lipases from Staphylococcus epidermidis as a catalyst in an aqueous environment. These esters were enzymatically synthesized to overcome the problems associated with chemical processes. This study showed that the S. epidermidis lipases could catalyze ester synthesis from decyl alcohol and fatty acids of different chain length. The wild-type and mutant lipases (M419A and V649I) could efficiently catalyze the synthesis of decyl alcohol esters of unsaturated fatty acids. In contrast, the yield of decyl laurate was better by wild-type and mutant enzyme V6491, but mutant enzyme M419A only favored the synthesis of decyl myristate. The esterification of oleic acid and various carbon-chain-length alcohols from ethanol to hexadecanol increased up to decanol by wild-type and M419A mutant enzymes and reached an optimum for dodecanol by V6491 mutant enzyme. The enzyme is potentially useful in food industries such as dairy product flavoring.

A study of cytokine gene polymorphisms and protein secretion in renal transplantation.

Although there is evidence that cytokine gene polymorphisms are associated with varying quantities of cytokine protein production, the exact role of these polymorphisms in allograft rejection remains unclear. In a previous study, we demonstrated a significant association between high IL-10 secretion in mixed lymphocyte culture (MLC), together with HLA mismatching for at least 4-6 antigens, with the occurrence of acute rejection following renal transplantation. We, therefore, wished to ascertain whether cytokine gene polymorphisms are associated with varying levels of protein secretion and/or allograft rejection in the same group of patients. Cytokine protein secretion in MLC for IL-4, IL-6, IL-10 and IFN-gamma was measured by ELISA in 49 patient-donor pairs. Protein secretion for the above cytokines was also measured in phytohaemagglutinin (PHA) stimulated cultures in 30 normal controls. In both patient and control groups, single nucleotide polymorphism analysis for IL-4 G(-590)T, IL-6 G(-174)C, IL-10 G(-1082)A, IL-10 C(-819)T, IL-10 C(-592)A, TNF-alpha G(-308)A and microsatellite analysis for IFNG (CA repeat) was performed. No correlation was found between cytokine gene polymorphisms and cytokine protein secretion in either mitogen stimulated cultures (control group) or MLC (patient group). In addition, no correlation was demonstrated between cytokine gene polymorphisms and renal allograft rejection.

Cytokine secretion in mixed lymphocyte culture: a prognostic indicator of renal allograft rejection in addition to HLA mismatching.

We have previously demonstrated significant inter-individual variations in cytokine protein secretion between normal individuals and patients prior to renal transplantation. In this study, pre-transplant patient vs. donor mixed lymphocyte cultures (MLC) were set up between 57 renal allograft patient/donor pairs, and secretion of cytokine protein (IL-2, IL-4, IL-6, IL-10 and IFN-gamma) into the culture supernatant measured by ELISA. Significant inter-individual variations in protein secretion in MLC were observed for all cytokines studied. Univariate analysis demonstrated that high levels of IFN-gamma and IL-10 in MLC and spontaneous IL-4, together with female donor sex and a high degree of HLA mismatching (especially HLA-DR) were significantly associated with rejection. However, multivariate analysis revealed the greatest risk of rejection (RR = 25.5, P = 0.003) was associated with a combination of high IL-10 secretion in MLC and mismatching for at least four HLA antigens (HLA-A, -B and -DR). It remains to be determined whether cytokine secretion in MLC is linked to cytokine gene polymorphisms. In future, assays for measuring either cytokine secretion or genetic polymorphisms may prove to be useful in aiding donor selection and tailoring immunosuppressive therapy.

Cloning and expression of a cDNA coding for catalase from zebrafish (Danio rerio).

A full-length complementary DNA (cDNA) clone encoding a catalase was amplified by the rapid amplication of cDNA ends-polymerase chain reaction (RACE-PCR) technique from zebrafish (Danio rerio) mRNA. Nucleotide sequence analysis of this cDNA clone revealed that it comprised a complete open reading frame coding for 526 amino acid residues and that it had a molecular mass of 59 654 Da. The deduced amino acid sequence showed high similarity with the sequences of catalase from swine (86.9%), mouse (85.8%), rat (85%), human (83.7%), fruit fly (75.6%), nematode (71.1%), and yeast (58.6%). The amino acid residues for secondary structures are apparently conserved as they are present in other mammal species. Furthermore, the coding region of zebrafish catalase was introduced into an expression vector, pET-20b(+), and transformed into Escherichia coli expression host BL21(DE3)pLysS. A 60-kDa active catalase protein was expressed and detected by Coomassie blue staining as well as activity staining on polyacrylamide gel followed electrophoresis.

Crystallization and preliminary X-ray crystallographic analysis of thioesterase I from Escherichia coli.

The Escherichia coli thioesterase I specifically catalyzes the deacylation of fatty acyl-CoA thioesters, especially those with long acyl groups (C(12)-C(18)). Single crystals of thioesterase I (E.C. 3. 1.2.2) from E. coli have been obtained using methoxypolyethylene glycol 5000 (PEG-MME 5K) as a precipitant at room temperature in 21 d. The crystals belong to the tetragonal space group P4(1)2(1)2 or its enantiomorph P4(3)2(1)2, with unit-cell parameters a = b = 50.85 (7), c = 171.5 (1) A. The crystals diffract to beyond 2.4 A resolution. There is one molecule of molecular weight 20.5 kDa in the asymmetric unit, with a solvent content of 55%.

Characterization of the dimer-monomer equilibrium of the papaya Copper/Zinc superoxide dismutase and its equilibrium shift by a single amino acid mutation.

The coding region of the copper/zinc superoxide dismutase (Cu/Zn SOD) cDNA from papaya fruit, Carica papaya L. cv. Tainong 2, was cloned into an expression vector, pET-20b(+). The Cu/Zn SOD was expressed in Escherichia coli and purified by His-tag technique. Two active forms of the enzyme (30% dimer and 70% monomer) in equilibrium were observed. The activity of the dimeric enzyme was higher than that of the monomeric form. The thermal inactivation rate constant K(d) values calculated for the dimer and monomer at 90 degrees C were -0.0203 and -0.0216 min(-1), and the half-lives for inactivation were 41.9 and 31.8 min, respectively. This indicated that the dimeric enzyme was more stable than its monomeric form. The dimerization of the enzyme was inhibited under acidic pH (below 3.0) or imidazole buffer (above 0.5 M), whereas it was not affected under alkaline pH (above 9.0). Both activity and forms of the enzyme were not affected by 1-4% SDS. Furthermore, the dimeric enzyme was much more resistant to proteolytic attack after 3 h of incubation at 37 degrees C with trypsin or chymotrypsin. In addition, mutation of the papaya Cu/Zn SOD at position 48 from Leu to Phe (L48F) affected the association of monomer, whereas a mutant with Lys substitution (L48K) at the same position tended to dissociate into monomeric form.

Analysis of the gene family encoding lipases in Candida rugosa by competitive reverse transcription-PCR.

Synthesis of multiple extracellular lipases in Candida rugosa has been demonstrated. However, it is difficult to characterize the expression spectrum of lip genes, since the sequences of the lip multigene family are very closely related. A competitive reverse transcription-PCR assay was developed to quantify the expression of lip genes. In agreement with the protein profile, the abundance of lip mRNAs was found to be (in decreasing order) lip1, lip3, lip2, lip5, and lip4. To analyze the effects of different culture conditions, the transcript concentrations for these mRNA species were normalized relative to the values for gpd, encoding glyceraldehyde-3-phosphate dehydrogenase. In relative terms, lip1 and lip3 were highly and constitutively expressed (about 10(5) molecules per microg of total RNA) whereas the other inducible lip genes, especially lip4, showed significant changes in mRNA expression under different culture conditions. These results indicate that differential transcriptional control of lip genes results in multiple forms of lipase proteins.

Multinuclear NMR resonance assignments and the secondary structure of Escherichia coli thioesterase/protease I: a member of a new subclass of lipolytic enzymes.

Escherichia coli thioesterase/protease I is a 183 amino acid protein with a molecular mass of 20,500. This protein belongs to a new subclass of lipolytic enzymes of the serine protease superfamily, but with a new GDSLS consensus motif, of which no structure has yet been determined. The protein forms a tetramer at pH values above 6.5 and exists as a monomer at lower pH values. Both monomer and tetramer are catalytically active. From analysis of a set of heteronuclear multidimensional NMR spectra with uniform and specific amino acid labeled protein samples, we have obtained near-complete resonance assignments of the backbone 1H, 13C and 15N nuclei (BMRB databank accession number 4060). The secondary structure of E. coli thioesterase/protease I was further deduced from the consensus chemical shift indices, backbone short- and medium-range NOEs, and amide proton exchange rates. The protein was found to consist of four beta-strands and seven alpha-helices, arranged in alternate order. The four beta-strands were shown to form a parallel beta-sheet. The topological arrangement of the beta-strands of -1x, +2x, +1x appears to resemble that of the core region of the alpha beta hydrolase superfamily, typically found in common lipases and esterases. However, substantial differences, such as the number of beta-strands and the location of the catalytic triad residues, make it difficult to give a definitive classification of the structure of E. coli thioesterase/protease I at present.

The International Society for Pediatric Neurosurgery 1972-1997. Some reflections from Edinburgh.

A personal review and recollection of the development of paediatric neurosurgery, as seen from Edinburgh, on the occasion of the twenty-fifth anniversary of the foundation of the International Society for Pediatric Neurosurgery.

The thioesterase I of Escherichia coli has arylesterase activity and shows stereospecificity for protease substrates.

A thioesterase I gene was recloned and sequenced from Escherichia coli strain JM109. The overexpressed, matured enzyme from JM109 was purified to homogeneity. The enzyme showed broad hydrolytic activity toward three kinds of substrates including acyl-CoAs, esters, and amino acid derivatives. The enzyme had a kcat/Km value of 0.363 s-1 microM-1, for a typical thioesterase I substrate, palmitoyl-CoA. The arylesterase activity of the enzyme was observed by its ability to hydrolyze several aromatic esters including alpha-naphthyl acetate, alpha-naphthyl butyrate, phenyl acetate, benzyl acetate, and eight p-nitrophenyl esters. In kinetic studies a chymotrypsin-like substrate (an amino acid derivative), N-carbobenzoxy-L-phenylalanine p-nitrophenyl ester (L-NBPNPE), was the best substrate for the enzyme with a catalytic efficiency (kcat/Km) of 4.00 s-1 microM-1, which was 23 times higher than that of the enantiomer D-NBPNPE (0.171 s-1 microM-1). It was concluded that the thioesterase I of E. coli had arylesterase activity and it possessed stereospecificity for protease substrates.

Studying the active site pocket of Staphylococcus hyicus lipase by site-directed mutagenesis.

Site-directed mutagenesis of a previously constructed, recombinant Staphylococcus hyicus lipase (49 kDa) showed that Val363 played a role in catalysis and substrate-binding. In comparison with wild type enzyme, the 64% and 89% decrease in the catalytic efficiency (kcat/Km) of the V363N and V363A enzymes, respectively, were largely caused by a 3.5- and 5.5-fold increase in the substrate-binding affinity (Km), respectively. In comparison with wild type enzyme, a G371A enzyme showed a 40% decrease in the Km, suggesting that G371 was important for substrate-binding specificity. Site-directed mutagenesis of the active site Asp559 revealed that in comparison with wild type enzyme, a D559E enzyme exhibited a 47% decrease in the kcat/Km but a twofold increase in the Km for p-nitrophenyl butyrate, suggesting that Asp-559, a component of the catalytic triad, was involved in substrate-specificity.