Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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 cells of Rhodospirillum rubrum and Thiocapsa roseopersicina grown in media containing glutamate and arginine, respectively, as well as under conditions of nitrogen fixation evolve H2 in the light. If the cultures were grown in media with NH4+, NO3-, urea, glutamine or asparagine, hydrogen photoevolution by the cells and acetylene reduction started after the lag-phase and proceeded at a low rate. Extracts of such cells did not display the activity of nitrogenase which could be assayed by the ATP-dependent evolution of H2 from dithionite. The data obtained confirm the fact that hydrogen photoevolution by purple bacteria involves nitrogenase whose synthesis is regulated (according to the action of glutamine) with the participation of glutamine synthetase. NH4+, glutamine and asparagine inhibit also hydrogen photoproduction by purple bacteria and acetylene photoreduction. However, they have no effect on hydrogen evolution in the dark by the cells of R. rubrum and T. roseopersicina in the presence of formiate or pyruvate, respectively, whereas carbon monoxide inhibits hydrogen production. Therefore, hydrogen production by purple bacteria in the dark must be catalyzed by hydrogenase.
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PMID:[Effect of nitrogen-containing compounds on hydrogen light emission and nitrogen fixation by purple bacteria]. 11 58

The properties of purified hydrogenase [EC 1.12.2.1] solubilized from particulate fraction of sonicated Desulfovibrio vulgaris cells are described. The enzyme was a brownish iron-sulfur protein of molecular weight 89,000, composed of two different subunits (mol. wt.: 28,000 and 59,000), and it contained 7-9 iron atoms and 7-8 labile sulfide ions. Molybdenum was not detected in the preparation. The absorption spectrum of the enzyme was characteristic of iron-sulfur proteins. The millimolar absorbance coefficients of the enzyme were about 164 at 280nm, and 47 at 400nm. The absorption spectrum of the enzyme in the visible region changed upon incubating the enzyme under H2 in the presence of cytochrome c3, but not in its absence. This spectral change was due to the reduction of the enzyme. The absorbance ratio at 400nm of the reduced and the oxidized forms of the enzyme was 0.66. The activity of the enzyme was hardly affected by metal-complexing agents such as cyanide, azide, 1,10-phenanthroline, etc., except for CO, which was a strong inhibitor of the enzyme. The activity was inhibited by SH-reagents such as p-chloromercuribenzenesulfonate. The enzyme was significantly resistant to urea, but susceptible to sodium dodecyl sulfate. These properties were very similar to those of clostridial hydrogenase [EC 1.12.7.1], in spite of differences in the acceptor specificity and subunit structure.
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PMID:Properties of purified hydrogenase from the particulate fraction of Desulfovibrio vulgaris, Miyazaki. 18 72

An investigation was made of certain factors involved in the formation of hydrogen gas, both in an anaerobic environment (argon) and in air, by the blue-green alga Anabaena cylindrica. The alga had not been previously adapted under hydrogen gas and hence the hydrogen evolution occurred entirely within the nitrogen-fixing heterocyst cells; organisms grown in a fixed nitrogen source, and which were therefore devoid of heterocysts, did not produce hydrogen under these conditions. Use of the inhibitor dichlorophenyl-dimethyl urea showed that hydrogen formation was directly dependent on photosystem I and only indirectly dependent on photosystem II, consistent with heterocysts being the site of hydrogen formation. The uncouplers carbonyl cyanide chlorophenyl hydrazone and dinitrophenol almost completely inhibited hydrogen formation, indicating that the process occurs almost entirely via the adenosine 5'-triphosphate-dependent nitrogenase. Salicylaldoxime also inhibited hydrogen formation, again illustrating the necessity of photophosphorylation. Whereas hydrogen formation could usually only be observed in anaerobic, dinitrogen-free environments, incubation in the presence of the dinitrogen-fixing inhibitor carbon monoxide plus the hydrogenase inhibitor acetylene resulted in significant formation of hydrogen even in air. Hydrogen formation was studied in batch cultures as a function of age of the cultures and also as a function of culture concentration, in both cases the cultures being harvested in logarithmic growth. Hydrogen evolution (and acetylene-reducing activity) exhibited a distinct maximum with respect to the age of the cultures. Finally, the levels of the protective enzyme, superoxide dismutase, were measured in heterocyst and vegetative cell fractions of the organism; the level was twice as high in heterocyst cells (2.3 units/mg of protein) as in vegetative cells (1.1 units/mg of protein). A simple procedure for isolating heterocyst cells is described.
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PMID:Anaerobic and aerobic hydrogen gas formation by the blue-green alga Anabaena cylindrica. 41 67

The hydrogenase from Paracoccus denitrificans, which is an intrinsic membrane protein, has been solubilised from membranes by Triton X-100. The partial specific volume of the solubilised protein has been determined using sucrose density gradient centrifugation in H2O and 2H2O. The values of the specific volumes of hydrogenase, measured in the presence or absence of Triton X-100, are 0.73 and 0.74 ml . g-1, respectively, indicating that hydrogenase binds much less than one micelle of Triton X-100. The sedimentation coefficient of hydrogenase is increased from 10.4 S to 15.9 S on removal of detergent. The Stokes' radius of hydrogenase, determined by gel filtration on Sepharose 6B, is 5.5 nm in the presence of Triton X-100 compared to 6.7 nm in the absence of detergent. The apparent molecular weight therefore increases from 242,500 to 466,000 on removal of detergent. In the presence of urea and sodium dodecylsulphate, the hydrogenase has an apparent molecular weight of 63,000. The enzyme therefore behaves as a non-covalently linked tetramer in the presence of Triton X-100. Removal of Triton X-100 results in association of tetramers to form octamers.
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PMID:Hydrodynamic parameters of the detergent-solubilised hydrogenase from Paracoccus denitrificans. 47 60

Normotensive, Sprague-Dawley (S-D) and spontaneously hypertensive (SH) rats were subjected to aortic ligature. The systolic blood pressure of S-D rats was increased by +/- 80 mm Hg, whereas the blood pressure of SH rats with pre-existent hypertension increased only slightly, +/- 9 mm Hg. The S-D rats developed myocardial and renal infarcts as well as polyarteritis nodosa; the SH rats developed testicular and microadrenocortical infarcts only. Aortic-ligated S-D rats had elevated creatine phosphokinase, serum glutamic-oxaloacetic transaminase, serum glutamic-pyruvic transaminase, and lactic hydrogenase levels and manifested hyperglycemia, hypercholesterolemia, and elevated blood urea nitrogen (BUN) levels. Corticosterone levels increased in aortic-ligated S-D rats but decreased in SH rats. Collateralization about the site of aortic ligature appeared to be the same in both strains. It is suggested that the acutely induced hypertension in S-D rats rather than SH rats and differences in adrenal steroidogenesis between the two strains would best account for the dichotomous cardiovascular response to aortic constriction.
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PMID:Diverse cardiovascular responses to aortic constriction in normotensive Sprague-Dawley versus spontaneously hypertensive rats. 50 90

Pleiotropic mutants of Alcaligenes eutrophus with the phenotype Hno- have been characterized previously. They are deficient in several diverse metabolic activities, including hydrogen oxidation, nitrate and urea assimilation, denitrification, and various substrate transport systems. Phenotypically similar mutants were identified among hydrogenase-deficient strains of Pseudomonas facilis. The Tn5-labeled hno gene was cloned from a genomic DNA library of A. eutrophus and used to identify the corresponding unimpaired wild-type DNA sequence. The recombinant plasmid pCH148 contained an insert of 12.3 kilobase pairs and was shown to restore the Hno+ phenotype to mutants of A. eutrophus and P. facilis. A cosmid isolated from a DNA library of P. facilis also exhibited intergeneric Hno-complementing activity. The cloned hno loci from both organisms showed DNA homology by Southern blot hybridization. A subclone of pCH148 which contained a 6.5-kilobase-pair insert was constructed. The resulting hybrid, pCH170, not only was able to complement Hno- mutants but also relieved glutamine auxotrophy in NtrA- mutants of enteric bacteria. This suggests that the hno gene product from A. eutrophus is functionally similar to the NtrA protein, which has been identified as a novel sigma factor (sigma 54) of RNA polymerase.
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PMID:An rpoN-like gene of Alcaligenes eutrophus and Pseudomonas facilis controls expression of diverse metabolic pathways, including hydrogen oxidation. 253 72

The detrimental effects of excessive Ni on plant growth have been well known for many years. More recent evidence indicates that Ni is required in small amounts for normal plant growth and development. Ni is an essential component of urease in plants and microorganisms. A deficiency of Ni in plants is reported to result in necrotic lesions in leaves in response to toxic accumulations of urea. Urease plays an essential role in mobilization of nitrogenous compounds in plants, a process that is especially important during seed germination and fruit formation when protein reserves are degraded into amino acids. Arginine, an abundant amino acid in plants, when degraded produces urea as a product and urease is needed for urea utilization. Theories of urea formation during allantoin degradation in Glycine max have been recently refuted. In G. max ureides apparently are metabolized via an amidohydrolase reaction with subsequent degradation of ureidoglycine, yielding glyoxylate, NH+4 and CO2. No evidence is available for the formation of urea in this pathway. Nitrogen-fixing symbionts, such as Rhizobium and Bradyrhizobium, contain two known Ni enzymes: urease and hydrogenase. Optimum growth of nodulated legumes and actinorhizal plants may depend on an adequate supply of Ni to meet the requirements of the Ni-requiring enzymes in host plants and endophytes. The seeds of severely Ni-deficient Hordeum are completely inviable, thus providing conclusive evidence for the essentiality of Ni for this species. The evidence indicates that Ni must be added to the list of micronutrient elements generally required by plants.
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PMID:Nickel as a micronutrient element for plants. 307 27

Electrophoretic and isoelectrofocusing behavior of the hydrogenase from Thiocapsa roseopersicina under various conditions revealed remarkable properties of this enzyme: there are two active forms which differ in their molecular masses as well as in oxygen sensitivity; the apparent molecular masses of the active hydrogenase forms (90 and 49 kDa) differ considerably from those in the inactive state (64, 34, and 15 kDa); the active forms and some of the inactivated ones can be transformed into each other reversibly; urea can unfold the 64 and 34 kDa proteins but not the 49 kDa form at room temperature; the pI of these proteins are different in the presence of urea. The results suggest large rearrangements in the hydrogenase protein structure which are associated with the enzymatically active and inactive states. It is concluded that reversible formation of disulfide bonds cannot be the major cause for maintaining the enzyme conformation. Strong hydrophobic interactions are suggested to be primarily responsible for the structural stability and for the rearrangements.
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PMID:Protein structural changes associated with active and inactive states of hydrogenase from Thiocapsa roseopersicina. 308 16

Chemical modification of the NAD+-dependent hydrogenase from the hydrogen oxidizing bacterium Alcaligenes eutrophus Z1 results in considerable enzyme stabilization towards urea and temperature induced inactivation. The stabilizing effect was shown to originate from the suppression of hydrogenase tetramer dissociation. The magnitudes of the stabilizing effects (5-fold and more) were in agreement with the values predicted on the basis of the enzyme thermoinactivation mechanism postulated earlier. Hydrophobic interactions are considered to be critical for the stability of the enzyme quaternary structure. Various methods of hydrogenase immobilization were tested. The enzyme was immobilized with a high retention of activity on aminated silochrom via its carboxylic groups.
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PMID:NAD+-dependent hydrogenase from the hydrogen oxidizing bacterium Alcaligenes eutrophus Z1. Stabilization against temperature and urea induced inactivation. 308 15

1. The kinetic and metabolic properties of lactate dehydrogenase isoenzyme LDH(x) from human sperm cells and rat testes were studied. 2. LDH(x) shows a sensitivity to inhibition by stilboestrol diphosphate, urea and guanidinium chloride different from that of the LDH-H(4) and LDH-M(4) isoenzymes. 3. About 10 and 20% of the total lactate dehydrogenase activity of testes and sperm cells respectively were associated with particulate fractions. In sperm cells 11% was localized in the middle piece and 18.8% in the head fraction. LDH(x) was found in all particulate fractions of sperm cells. The middle piece contained 41.0% of total LDH(x) activity and showed high succinate dehydrogenase activity. 5. The pH-dependence of lactate/pyruvate and NAD(+)/NADH concentration ratios were estimated. Lactate dehydrogenase in sperm cells has maximal activity with NADH as coenzyme at pH7.5 and with NADPH as coenzyme at pH6.0. At pH6.0 a 10% greater oxidation of NADPH than of NADH was found. At acid pH lactate hydrogenase may function as an enzyme bringing about transhydrogenation from NADPH to NAD(+). 6. In agreement with the stoicheiometry of the lactate de- hydrogenase reaction, the lactate/pyruvate concentration ratio decreased with increasing pH. 7. The lactate/pyruvate and NAD(+)/NADH concentration ratios were estimated with glucose, fructose and sorbitol as substrates and as a function of time after addition of these substrates. During a 20min. period after the addition of the substrates, changes in lactate/pyruvate and NAD(+)/NADH concentration ratios were noticed. Increasing concentration of the substrates mentioned gave rise to asymptotic increases in lactate and pyruvate. 8. Sorbitol did not act as a substrate for LDH(x). 9. The findings described are consistent with the idea that LDH(x) is different from other known lactate dehydrogenase isoenzymes, but that it has a metabolic function similar to that of the isoenzymes of other tissues.
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PMID:Lactate dehydrogenase isoenzymes of sperm cells and tests. 430 63


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