Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.12.7.2 (hydrogenase)
 3,522 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The hydrogenase from T. roseopersicina is highly resistant to the effects of urea (8 M), Me2SO (20%) and DS-Na (1%), while inactivation of the hydrogenase from Rhodopseudomonas capsulata occurs in the presence of 0.1% DS-Na. The higher the purification level of T. roseopersicina hydrogenase preparation, the higher stability it possesses (T 1/2 = 60 days, 24 degrees). The hydrogenase inactivation at 80 degrees under anaerobic conditions occurs in one stage according to the equation of first-order-reaction (k1i = 7.10(-5) sec-1), while under aerobic conditions it has two stages with a decrease in the rate of this process in the second stage (k2i = 1.8 . 10(-6) sec-1). Glycerol and NaCl do not stabilize the T. roseopersicina hydrogenase. The rate of thermal inactivation of the hydrogenase bound to the membranes, DEAE-cellulose or phenylsepharose is higher than that of the soluble enzyme. The considerable decrease of the thermal stability of the enzyme is caused by the thiol reagents: they cause irreversible denaturation of the enzyme. The hydrogenase partly inactivated under aerobic conditions is reactivated in the presence of Na2S2O4. The data obtained indicate the important role of disulphide bonds in stabilization of T. roseopersicina hydrogenase.
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PMID:[Stability of hydrogenase from the purple sulfur bacteria Thiocapsa roseopersicina]. 704 14

The metabolism of Clostridium butyricum was manipulated at pH 6.5 and in phosphate-limited chemostat culture by changing the overall degree of reduction of the substrate using mixtures of glucose and glycerol. Cultures grown on glucose alone produced only acids (acetate, butyrate, and lactate) and a high level of hydrogen. In contrast, when glycerol was metabolized, 1,3-propanediol became the major product, the specific rate of acid formation decreased, and a low level of hydrogen was observed. Glycerol consumption was associated with the induction of (i) a glycerol dehydrogenase and a dihydroxyacetone kinase feeding glycerol into the central metabolism and (ii) an oxygen-sensitive glycerol dehydratase and an NAD-dependent 1,3-propanediol dehydrogenase involved in propanediol formation. The redirection of the electron flow from hydrogen to NADH formation was associated with a sharp decrease in the in vitro hydrogenase activity and the acetyl coenzyme A (CoA)/free CoA ratio that allows the NADH-ferredoxin oxidoreductase bidirectional enzyme to operate so as to reduce NAD in this culture. The decrease in acetate and butyrate formation was not explained by changes in the concentration of phosphotransacylases and acetate and butyrate kinases but by changes in in vivo substrate concentrations, as reflected by the sharp decrease in the acetyl-CoA/free CoA and butyryl-CoA/free CoA ratios and the sharp increase in the ATP/ADP ratio in the culture grown with glucose and glycerol compared with that in the culture grown with glucose alone. As previously reported for Clostridium acetobutylicum (L. Girbal, I. Vasconcelos, and P. Soucaille, J. Bacteriol. 176:6146-6147, 1994), the transmembrane pH of C. butyricum is inverted (more acidic inside) when the in vivo activity of hydrogenase is decreased (cultures grown on glucose-glycerol mixture). For both cultures, the stoichiometry of the H(+) ATPase was shown to remain constant and equal to 3 protons exported per molecule of ATP consumed.
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PMID:Regulation of carbon and electron flow in Clostridium butyricum VPI 3266 grown on glucose-glycerol mixtures. 1116 Jan 7

Glycerol is an attractive carbon source for biofuel production since it is cheap and abundant due to the increasing demand for renewable and clean energy sources, which includes production of biodiesel. This research aims to enhance hydrogen production by Escherichia coli from glycerol by manipulating its metabolic pathways via targeted deletions. Since our past strain, which had been engineered for producing hydrogen from glucose, was not suitable for producing hydrogen from glycerol, we rescreened 14 genes related to hydrogen production and glycerol metabolism. We found that 10 single knockouts are beneficial for enhanced hydrogen production from glycerol, namely, frdC (encoding for furmarate reductase), ldhA (lactate dehydrogenase), fdnG (formate dehydrogenase), ppc (phosphoenolpyruvate carboxylase), narG (nitrate reductase), focA (formate transporter), hyaB (the large subunit of hydrogenase 1), aceE (pyruvate dehydrogenase), mgsA (methylglyoxal synthase), and hycA (a regulator of the transcriptional regulator FhlA). On that basis, we created multiple knockout strains via successive P1 transductions. Simultaneous knockouts of frdC, ldhA, fdnG, ppc, narG, mgsA, and hycA created the best strain that produced 5-fold higher hydrogen and had a 5-fold higher hydrogen yield than the parent strain. The engineered strain also reached the theoretical maximum yield of 1 mol H2/mol glycerol after 48 h. Under low partial pressure fermentation, the strain grew over 2-fold faster, indicating faster utilization of glycerol and production of hydrogen. By combining metabolic engineering and low partial pressure fermentation, hydrogen production from glycerol was enhanced significantly.
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PMID:Metabolic engineering of Escherichia coli to enhance hydrogen production from glycerol. 2461 84