Rational design of L-arabinose isomerase from Lactobacillus fermentum and its application in D-tagatose production / 生物工程学报

L-arabinose isomerase (L-AI) is the key enzyme that isomerizes D-galactose to D-tagatose. In this study, to improve the activity of L-arabinose isomerase on D-galactose and its conversion rate in biotransformation, an L-arabinose isomerase from Lactobacillus fermentum CGMCC2921 was recombinantly expressed and applied in biotransformation. Moreover, its substrate binding pocket was rationally designed to improve the affinity and catalytic activity on D-galactose. We show that the conversion of D-galactose by variant F279I was increased 1.4 times that of the wild-type enzyme. The Km and kcat values of the double mutant M185A/F279I obtained by superimposed mutation were 530.8 mmol/L and 19.9 s-1, respectively, and the catalytic efficiency was increased 8.2 times that of the wild type. When 400 g/L lactose was used as the substrate, the conversion rate of M185A/F279I reached a high level of 22.8%, which shows great application potential for the enzymatic production of tagatose from lactose.

[Expression of genes 1-deoxy-d-xyhilose 5-phosphate reductoisomerase [dxr], sabinen synthase [tctpsl] and a- terpineol synthase [tctpss] and its relation to thymol and carvaerol biosynthesis in thymus vulgaris under water deficit stress]

Background: Thymol and Carvaerol are the two important secondary metabolites from Thymus vulgaris that productions of them are controlled by genetic and environmental factors

Objective: Evaluation of Water stress effects on expression of three important genes of thymol and carvacrol biosynthetic pathway and also physiological and phytochemical properties of Thymus vulgaris

Methods: The present study was conducted in a randomized complete block design with 4 treatments and 3 replications in Institute of Medicinal Plants, ACECR, Karaj

For this purpose, the treatments were selected as control [FC], 70% of FC, 40% of FC, and 20% of FC. Gene expression was studied using real-time PCR method, and HPLC was applied to essence analysis. Also physiological characteristic including chlorophyll content, relative water content, electrolyte leakage percentage and carotenoids content were analyzed

Results: The results revealed that water stress significantly influenced the gene expression [P< 0.05]. The highest gene expression of DXR and TctpsS was observed in 70% of FC, while the highest one of TvTPSl was recorded in 40% of FC. Moreover, the maximum thymol and carvacrol was found in 70% of FC. In other hand the highest chlorophyll content and corotenoids content were obtained in 100% and 70% of FC respectively. Also there were not significant differences between treatments for relative water content and electrolyte leakage percentage

Conclusion: The 70% of FC through influencing of genes in the firs and last of MEP pathway increased thymol and carvacrol production

Expression, purification and characterization of arabinose-5-phosphate isomerase from Arabidopsis thaliana / 生物工程学报

Arabinose-5-phosphate isomerase (KdsD) is the first key limiting enzyme in the biosynthesis of 3-deoxy-D-manno-octulosonate (KDO). KdsD gene was cloned into prokaryotic expression vector pET-HTT by seamless DNA cloning method and the amount of soluble recombinant protein was expressed in a soluble form in E. coli BL21 (DE3) after induction of Isopropyl β-D-1-thiogalactopyranoside (IPTG). The target protein was separated and purified by Ni-NTA affinity chromatography and size exclusion chromatography, and its purity was more than 85%. Size exclusion chromatography showed that KdsD protein existed in three forms: polymers, dimmers, and monomers in water solution, different from microbial KdsD enzyme with the four polymers in water solution. Further, the purified protein was identified through Western blotting and MALDI-TOF MASS technology. The results of activity assay showed that the optimum pH and temperature of AtKdsD isomerase activities were 8.0 and 37 ℃, respectively. The enzyme was activated by metal protease inhibitor EDTA (5 mmol/L) and inhibited by some metal ions at lower concentration, especially with Co²⁺ and Cd²⁺ metal ion. Furthermore, when D-arabinose-5-phosphate (A5P) was used as substrate, Km and Vmax of AtKdsD values were 0.16 mmol/L, 0.18 mmol/L·min. The affinity of AtKdsD was higher than KdsD in E. coli combined with substrate. Above results have laid a foundation for the KdsD protein structure and function for its potential industrial application.

Homologous human milk supplement for very low birth weight preterm infant feeding / Aditivo homólogo para a alimentação do recém-nascido pré-termo de muito baixo peso

OBJECTIVE: To develop a homologous human milk supplement for very low-birth weight infant feeding, using an original and simplified methodology, to know the nutritional composition of human milk fortified with this supplement and to evaluate its suitability for feeding these infants. METHODS: For the production and analysis of human milk with the homologous additive, 25 human milk samples of 45mL underwent a lactose removal process, lyophilization and then were diluted in 50mL of human milk. Measurements of lactose, proteins, lipids, energy, sodium, potassium, calcium, phosphorus and osmolality were performed. RESULTS: The composition of the supplemented milk was: lactose 9.22±1.00g/dL; proteins 2.20±0.36g/dL; lipids 2.91±0.57g/dL; calories 71.93±8.69kcal/dL; osmolality 389.6±32.4mOsmol/kgH2O; sodium 2.04±0.45mEq/dL; potassium 1.42±0.15mEq/dL; calcium 43.44±2.98mg/dL; and phosphorus 23.69±1.24mg/dL. CONCLUSIONS: According to the nutritional contents analyzed, except for calcium and phosphorus, human milk with the proposed supplement can meet the nutritional needs of the very low-birth weight preterm infant. .

OBJETIVO: Elaborar com metodologia original e simplificada um aditivo homólogo do leite humano para a alimentação do recém-nascido de muito baixo peso, conhecer a composição nutricional do leite humano fortificado com esse aditivo e avaliar sua adequação para a alimentação desses recém-nascidos. MÉTODOS: Para a produção e análise do leite humano com o aditivo homólogo, 25 amostras de 45 mL de leite humano passaram por processos de retirada de lactose, liofilização e foram diluídas em 50 mL de leite humano. Foram feitas dosagens de lactose, proteínas, lipídios, energia, sódio, potássio, cálcio, fósforo e osmolalidade. RESULTADOS: A composição do leite aditivado foi lactose 9,22 ± 1 g/dL; proteínas 2,20 ± 0,36 g/dL; lípides 2,91 ± 0,57 g/dL; calorias 71,93 ± 8,69 kcal/dL; osmolalidade 389,6 ± 32,4mOsmol/kgH2O; sódio 2,04 ± 0,45mEq/dL; potássio 1,42 ± 0,15mEq/dL; cálcio 43,44 ± 2,98 mg/dL; e fósforo 23,69 ± 1,24 mg/dL. CONCLUSÕES: De acordo com os teores nutricionais analisados, com exceção do cálcio e do fósforo, o leite humano com o aditivo proposto pode atender às necessidades nutricionais do recém-nascido pré-termo de muito baixo peso. .

Roles of reactive oxygen species in Streptomyces pactum Act12-induced tanshinone production in Salvia miltiorrhiza hairy roots / 中国中药杂志

Our previous research indicated that the Streptomyces pactum Act12 (Act12) had a certain promotional effect on tanshinone accumulation and up-regulated the expression of genes 3-hydroxy-3-methyglutaryl-CoA reductase (HMGR) and 1-deoxy-d-xylulose-5-phosphate reductoisomerase (DXR) in Salvia miltiorrhiza hairy roots. This study focuses on the roles of reactive oxygen species in S. pactum Act12-induced tanshinone production in S. miltiorrhiza hairy roots. The 4% Act12, 4% Act12 + CAT and 4% Act12 + SOD were added to S. miltiorrhiza hairy root and subcultured for 21 days, the dry weight, contents of reactive oxygen species, contents of tanshinones and expression of HMGR and DXR were determined at different harvest-time. The generation of reactive oxygen species (ROS) in S. miltiorrhiza hairy roots was triggered by 4% Act12 treatment. The relative expressions of genes HMGR and DXR in 4% Act12 treatment were 32.4 and 4.8-fold higher than those in the control. And the total tanshinone in the hairy roots was 10.2 times higher than that of the control. The CAT and SOD could significantly inhibit the ROS accumulation and relative expressions of genes HMGR and DXR in 4% Act12 treatment, which induced the total tanshinone content was decreased by 74.6% comparing with the 4% Act12 treatment. ROS mediated Act12-induced tanshinone production. The Act12 may be via the ROS signal channel to activate the tanshinone biosynthesis pathways. Thereby the tanshinon content in hairy roots was increased.

Production of sugar syrup containing rare sugar using dual-enzyme coupled reaction system / 生物工程学报

Enzymatic conversion is very important to produce functional rare sugars, but the conversion rate of single enzymes is generally low. To increase the conversion rate, a dual-enzyme coupled reaction system was developed. Dual-enzyme coupled reaction system was constructed using D-psicose-3-epimerase (DPE) and L-rhamnose isomerase (L-RhI), and used to convert D-fructose to D-psicose and D-allose. The ratio of DPE and L-RhI was 1:10 (W/W), and the concentration of DPE was 0.05 mg/mL. The optimum temperature was 60 degrees C and pH was 9.0. When the concentration of D-fructose was 2%, the reaction reached its equilibrium after 10 h, and the yield of D-psicose and D-allose was 5.12 and 2.04 g/L, respectively. Using the dual-enzymes coupled system developed in the current study, we could obtain sugar syrup containing functional rare sugar from fructose-rich raw material, such as high fructose corn syrup.

Down-Regulation of Cellulose Synthase Inhibits the Formation of Endocysts in Acanthamoeba

Acanthamoeba cysts are resistant to unfavorable physiological conditions and various disinfectants. Acanthamoeba cysts have 2 walls containing various sugar moieties, and in particular, one third of the inner wall is composed of cellulose. In this study, it has been shown that down-regulation of cellulose synthase by small interfering RNA (siRNA) significantly inhibits the formation of mature Acanthamoeba castellanii cysts. Calcofluor white staining and transmission electron microscopy revealed that siRNA transfected amoeba failed to form an inner wall during encystation and thus are likely to be more vulnerable. In addition, the expression of xylose isomerase, which is involved in cyst wall formation, was not altered in cellulose synthase down-regulated amoeba, indicating that cellulose synthase is a crucial factor for inner wall formation by Acanthamoeba during encystation.

Genome wide association study of obesity / 中南大学学报(医学版)

Obesity is a great risk factor for type 2 diabetes and certain types of cancer, which become a major burden for public health worldwide. As a classic complex disease, obesity is regarded as the interaction of genetic and environmental factors. However, it is controversial which of these two factors have greater effect on obesity. Several genetic loci have recently been reported to contribute to the development of obesity reported in genome-wide association study (GWAS) these years. GWAS play an important role in complex disease research and explore the potential effect of genetic variance. To further understand the genetic influence on obesity risk, we reviewed and collected articles on Pubmed for genes that reported in recent GWAS. We summarized the publications in GWAS and found 49 candidate genes, which were strongly suggested to relate to obesity risk in human. Despite the findings of this and other similar, contemporary research projects, much of the single nucleotide polymorphism details and underlying mechanism in this field of study remains, to a great extent, unknown. As a result, future studies are needed for obesity risk in human beings.

Effects on Salvia miltiorrhiza hairy roots of tanshinones content accumulation after treated with fosmidomycin / 中国中药杂志

Fosmidomycin (100 micromol x L(-1)) which is the effective inhibitor of DXR, key enzyme in terpenoid MEP pathway, was used to treat with hairy roots of Salvia miltiorrhiza. The treated roots were harvested at 2, 4, 6, 8, 10, 16 and 21 d, mRNA level of SmDXR and tanshinone content in treated and negative control groups were detected. Results found that, after treated with fosmidomycin, color of S. miltiorrhiza hairy roots grew pale gradually comparing with controls; mRNA level of SmDXR in hairy roots varied as a shape of parabolic and the highest value achieved at the sixth day after treatment, then it decreased gradually; Content of four kinds of tanshinones were detected. Among of the four kinds of tanshinones, Tanshinone I content changed relatively little, while content of dihydrotanshinone I, cryptotanshinone and tanshinone II (A) decreased gradually in 21 days. The content of total tanshinones in NC groups was 5, 63 times more than FOS-treated roots in the 21th day. The previous results showed that SmDXR played an important role in the accumulation of tanshinone content in MEP pathway. Once the mRNA level of SmDXR was suppressed, the accumulation of secondary metabolites will be significantly affected.

Bioconversion of D-fructose to D-allose by novel isomerases / 生物工程学报

Rare sugar is a kind of important low-energy monosaccharide that is rarely found in nature and difficult to synthesize chemically. D-allose, a six-carbon aldose, is an important rare sugar with unique physiological functions. It is radical scavenging active and can inhibit cancer cell proliferation. To obtain D-allose, the microorganisms deriving D-psicose 3-epimerase (DPE) and L-rhamnose isomerase (L-RhI) have drawn intense attention. In this paper, DPE from Clostridium cellulolyticum H10 was cloned and expressed in Bacillus subtilis, and L-RhI from Bacillus subtilis 168 was cloned and expressed in Escherichia coli BL21 (DE3). The obtained crude DPE and L-RhI were then purified through a HisTrap HP affinity chromatography column and an anion-exchange chromatography column. The purified DPE and L-RhI were employed for the production of rare sugars at last, in which DPE catalyzed D-fructose into D-psicose while L-RhI converted D-psicose into D-allose. The conversion of D-fructose into D-psicose by DPE was 27.34%, and the conversion of D-psicose into D-allose was 34.64%.

Screening of food-grade microorganisms for biotransformation of D-tagatose and cloning and expression of L-arabinose isomerase / 生物工程学报

L-Arabinose isomerase (L-AI) is an intracellular enzyme that catalyzes the reversible isomerization of D-galactose and D-tagatose. Given the widespread use of D-tagatose in the food industry, food-grade microorganisms and the derivation of L-AI for the production of D-tagatose is gaining increased attention. In the current study, food-grade strains from different foods that can convert D-galactose to D-tagatose were screened. According to physiological, biochemical, and 16S rDNA gene analyses, the selected strain was found to share 99% identity with Pediococcus pentosaceus, and was named as Pediococcus pentosaceus PC-5. The araA gene encoding L-AI from Pediococcus pentosaceus PC-5 was cloned and overexpressed in E. coli BL21. The yield of D-tagatose using D-galactose as the substrate catalyzed by the crude enzyme in the presence of Mn2+ was found to be 33% at 40 degrees C.

Cloning and expression regulation of 1-deoxy-D-xylulose-5-phosphate reductoisomerase cDNA from Alpinia officinarum / 中国中药杂志

The rhizome of Alpinia officinarum is a widely used Chinese herbal medicine. The essential oil in A. officinarum rhizome is mainly composed of 1, 8-cineole and other monoterpenes, as the major bioactive ingredients. In plants, monoterpenes are synthesized through the methylerythritol phosphate (MEP) pathway in the plastids, and 1-deoxy-D-xylulose 5-phosphate reductoisomerase (DXR) is an enzyme catalyzing a committed step of the MEP pathway. In the present study, the full-length cDNA encoding DXR was cloned from the rhizome of A. officinarum, using homology-based RT-PCR and rapid amplification of cDNA ends (RACE) techniques. The new cDNA was designated as AoDXR and submitted to GenBank to be assigned with an accession number HQ874658. The full-length cDNA of AoDXR was 1 670 bp containing a 1 419 bp open reading frame encoding a polypeptide of 472 amino acids with a calculated molecular mass of 51.48 kDa and an isoelectric point of 6.15. Bioinformatic analyses revealed that AoDXR showed extensive homology with DXRs from other plant species and contained a conserved plastids transit peptide, a Pro-rich region and two highly conserved NADPH-binding motifs in its N-terminal region characterized by all plant DXRs. The phylogenetic analysis revealed that AoDXR belonged to angiosperm DXRs. The structural modeling of AoDXR showed that AoDXR had the typical V-shaped structure of DXR proteins. The tissue expression pattern analysis indicated that AoDXR expressed strongly in leaves, weak in rhizomes of A. officinarum. Exogenous methyl jasmonate (MeJA) could enhance the expression of AoDXR and the production of 1, 8-cineole in A. officinarum rhizomes. The cloning and characterization of AoDXR will be helpful to reveal the molecular regulation mechanism of monoterpene biosynthesis in A. officinarum and provides a candidate gene for metabolic engineering in improving the medicinal quality of A. officinarum rhizome.

Analysis of the binding domain of hydroxypyruvate isomerase homologues in hypertrophic scar fibroblasts / 中华烧伤杂志

<p><b>OBJECTIVE</b>To explore the binding domain of hydroxypyruvate isomerase homologues (HYI) in the interaction with protein P311 in hypertrophic scar fibroblasts (Fb).</p><p><b>METHODS</b>(1) P 311 was amplified by PCR using plasmid pMD18-T-P 311 as template. The total RNA of hypertrophic scar Fb was extracted by Trizol to amplify HYI with RT-PCR. Recombinant vectors pGADT7-P 311 and pGBKT7-HYI were constructed by double-enzyme digestion, and they were verified by PCR and sequencing. The secondary structure of protein HYI was analyzed with software Prot Seale and HNN. Fragments of HYI-1 (1-447 bp), HYI-2 (247-447 bp), HYI-3 (1-279 bp), and HYI-4 (247-654 bp) were amplified based on the result of software analysis. And then the recombinant vectors pGBKT7-HYI-1, 2, 3, and 4 were constructed by double-enzyme digestion and verified by PCR and sequencing. (2) AH109 yeast cells were transformed into competent cells by lithium acetate method and divided into 7 groups roughly in the same amount, including HYI full length, HYI-1, HYI-2, HYI-3, and HYI-4 hybrid groups, positive control group, and negative control group. Cells in the first five groups were respectively transformed with recombinant vector pGBKT7-HYI full length, pGBKT7-HYI-1, pGBKT7-HYI-2, pGBKT7-HYI-3, pGBKT7-HYI-4 and recombinant vector pGADT7-P 311, and that in the rest two groups were transformed with recombinant vectors pGBKT7-53 and pGADT7-RecT, pGADT7-RecT and pGBKT7-Lam by polyethyleneglycol/lithium acetate method. Immediately after transformation, a part of the transformed cells in each group was spread onto the medium lacking leucine, tryptophan, adenine, and histidine (briefly called four-factor lacking medium), and another portion of the cells was spread onto the medium lacking leucine and tryptophan (briefly called two-factor lacking medium). After 3 to 6 days' culture, the growth of yeast was observed, and the expression of β-galactosidase of yeast was detected by color reaction with 5-bromo-4-chloro-indolyl-β-D-galactopyranoside.</p><p><b>RESULTS</b>(1) Cloned P 311 and the reported P 311 (GenBank ID hsu36189) had the same sequence. The A base at 496 bp in reported HYI (GenBank ID AY775560) was replaced by G base as found in cloned HYI. It was verified that the insert segment of each recombinant vector was correct. (2) Among those 216 amino acids which composed the protein HYI, 101 amino acids might form α helices, 90 amino acids might form random coils, 25 amino acids might form extended-chains as revealed in the simulated structure analysis by computer. (3) Cloned segments HYI-1, 2, 3, 4 showed expected lengths. It was verified that the insert segment of each recombinant vector was correct. (4) Except for strains in negative control group which did not show growth on four-factor lacking medium, all strains in other groups grew on both kinds of media, and growth of colonies was less in HYI-2 (with the fewest number of α helices) and HYI-3 hybrid groups. (5) Positive expression of β-galactosidase was observed in strains of all groups growing on four-factor lacking medium except for the HYI-2 hybrid group. No expression of β-galactosidase was observed in strains of negative control group which grew on two-factor lacking medium.</p><p><b>CONCLUSIONS</b>Protein HYI may closely bind with protein P311 by α helix, which plays an important role in fibroblast-to-myofibroblast transdifferentiation in hypertrophic scar.</p>

Progress in the sequence and structure properties, thermostability mechanism and molecular modification of xylose isomerase: a review / 生物工程学报

With the development of low-carbon economy and renewable resource, fermentation of the pentose sugar xylose to produce ethanol becomes a very hot topic. The recombinant Saccharomyces cerevisiae can be constructed by expressing heterologous xylose isomerase (XI). Because Thermus thermophilus XI (TthXI) does not need cofactor, it has been developed for establishing the utilization pathway of xylose in S. cerevisiae. In this article, we reviewed the progress on xylose isomerase. We first introduced the primary properties, sequence and structure characters of xylose isomerase, and discussed its thermostability. The molecular modification of xylose isomerase, including of substrate specificity and thermostability were discussed in detail. Meanwhile, combined with our own research, we also discussed how to improve the xylose isomerase activity at room temperature. Finally, we suggested perspectives of xylose isomerase.

Biochemical characterization of N-methyl N'-nitro-N-nitrosoguanidine-induced cadmium resistant mutants of Aspergillus niger.

Two cadmium resistant mutants (Cd1 and Cd2) of Aspergillus niger, among the six isolated by mutagenization with N-methyl N'-nitro-N-nitrosoguanidine (MNNG) at pH 6.4 were selected for the study. Analysis of lipid composition of the mutants and the wildtype indicated that total lipid as well as individual lipids of the cadmium resistant mutants were changed as compared with that of the wildtype. The increased activities of metal-lothionein and reduced activities of D-xylose isomerase and L-phenylalanine ammonia lyase in cell free extract of the cadmium resistant mutants suggested that mutants could allow high concentration of cadmium salt as compared with that of the wildtype. The respiratory activity and intracellular as well as extracellular Cd2+ concentration of the mutants reflected the high tolerance of the Cd mutants to cadmium ion.

Cloning and analysis of cDNA encoding key enzyme gene (dxr) of the non-MVA pathway in Taxus chinensis cells / 生物工程学报

Two distinct routes (classical mevalonate pathway and a novel mevalonate-independent pathway) are utilized by plants for the biosynthesis of isopentenyl diphosphate, the universal precursor of isoprenoids (Fig. 1). Present researches indicated that taxol was synthesized mainly via non-mevalonate pathway, but not genetic evidence was showed. The second step in non-mevalonate pathway involves an intramolecular rearrangement and subsequent reduction of deoxyxylulose phosphate to yield 2-C-methyl-D-erythritol-4-phosphate, and 1-Deoxy-D-xylulose-5-phosphate reductoisomerase (DXR) with responsibility for this reaction was considered as a key enzyme. As a tool for the isolation of genes in terpenoid biosynthesis in plants, total RNA was prepared from Taxus chinensis suspension cells, a cell type highly specialized for diterpene (taxol). A reverse transcription-PCR strategy based on the design of degenerated oligonucleotides was developed for isolating the gene encoding a gymnosperm homolog of this enzyme from Taxus chinensis. Through sequence analysis by Blast P online, the resulting cDNA showed highly homologous to 1-deoxy-D-xylulose 5-phosphate reductoisomerases, with 95% identification compared with Arabidopsis thaliana (Q9XFS9), 94% with Mentha x piperita (Q9XESO), 80% with Synechococcus elongatus (Q8DK30), 78% with Synechocystis sp. PCC 6803 (Q55663) and Nostoc sp. PCC 7120 (Q8YP49), and 73% with Synechococcus leopoliensis (Q9RKT1). Deduced amino acid sequences were also analyzed by PROSITE, ClustalX (1.81) and Phylio (3.6 alpha), and data present evidence for the existence of this deoxyxyluose phosphate reductoisomerase in Taxus chinensis. This is the first report of the dxr gene cloned from gymnosperm.

Overexpression and detection of the mutated glucose isomerase GIG138P and GIG138P-G247D in Streptomyces lividans / 生物工程学报

The shuttle expression vectors pHZGI1 and pHZGI2 were successfully constructed by inserting structural genes of GI containing single mutated site G138P and double mutated site G138P-G247D into E. coli-Streptomyces shuttle vector pHZ-1272, respectively. Then they were transformed into S. lividans TK54 strain by protoplast transformation. SDS-PAGE indicated that two shuttle vectors in TK54 strain expressed obviously specific bands at 42.5 kD after inducted by 2 micrograms/mL thiostrepton. Optical densitometric scan showed that the content of the mutant enzymes GIG138P and GIG138P-G247D were about 19% and 22% of dissoluble proteins, respectively. Western blotting farther proved that GIG138P and GIG138P-G247D were expressed in S. lividans TK54.

Channeling of the intermediates and catalytic facilitation to Rubisco in a multienzyme complex of Calvin cycle enzymes.

Calvin cycle multienzyme complex, consisting of phosphoriboisomerase, phosphoribulokinase and ribulose-1,5-bisphosphate carboxylase (Rubisco), shows ribose-5-phosphate + ATP dependent CO2 fixation activity with a small but discernible lag. Transient time analysis showed that the lag at pH 7 was independent of multienzyme concentration and was significantly lower than the expected transient time calculated from Km and Vmax of the individual enzymes, indicative of channeling of the intermediates in the enzyme complex. Channeling of ribulose-1,5-bisphosphate was found to offer a catalytic advantage to Rubisco. Rubisco shows a decrease in activity during catalysis in ribulose-1,5-bisphosphate dependent CO2 fixation reaction, due to the formation of the catalytic inhibitor. Such a decrease of Rubisco activity was not observed in ribose-5-phosphate + ATP dependent CO2 fixation reaction and the catalytic inhibitor was also not detected. These results suggested that the intermediates are channeled in the complex and channeling offers a catalytic facilitation to Rubisco.

Photoprotection of ultraviolet light irradiated E. Coli. B/r cells.

Ultraviolet irradiated E. Coli. B/r cells recover from UV damage when the cells are kept in dark due to dark repair mechanism. Photoprotection by illumination of the cells in near UV light prior to the exposure to UV light increases the capacity of the cells to induce L-arabinose isomerase synthesis in response to inducer, L-arabinose. The survival of the cells is dependent on the UV dose. The increased synthesis of L-arabinose isomerase after photoprotection is due to the amount of cyclic AMP in the cells.