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)

1. The effect of poisons upon the photoreduction with hydrogen in Scenedesmus and similar algae has been studied. The poisons used were cyanide, hydroxylamine, dinitrophenol, and carbon monoxide, substances known to inhibit more or less specifically certain enzymatic reactions. 2. It was found that quite generally one has to distinguish between the action of poisons upon the photoreduction in the stationary state, once this type of metabolism has been well established in the cells, and their effects on transition phenomena, on the "adaptation" and its reversal, the "turnback" from photoreduction to photosynthesis. 3. Cyanide inhibits photoreduction more strongly than it inhibits photosynthesis in the same algae. It is concluded that the mechanism of oxygen liberation, which is idle in photoreduction, is not very sensitive to cyanide. 4. Hydroxylamine in low concentrations is a powerful inhibitor of photosynthesis but has practically no influence on the rate of photoreduction. Consequently, it is assumed that it acts in photosynthesis mainly by inhibiting the evolution of oxygen. Greater concentrations of hydroxylamine clearly inhibit photoreduction, but diminish the rate to about one-half only. A greater degree of inhibition is obtained only by prolonged incubation. 5. Dinitrophenol was found to inhibit strongly the reduction of carbon dioxide, under aerobic as well as under anaerobic conditions. A stimulating effect of dinitrophenol can be demonstrated only with respiration or fermentation, not with photosynthesis. 6. Carbon monoxide interferes with all phases of the hydrogen metabolism in algae. It is supposed therefore to be a specific inhibitor for the hydrogenase system. 7. The "adaptation" to the hydrogen metabolism, which takes place if the algae are incubated anaerobically in hydrogen for several hours, is inhibited completely by very small amounts of cyanide. The adaptation reaction is more sensitive to cyanide than most of the other metabolic processes in the same cell. Correspondingly cyanide enhances the return to aerobic conditions, the "turnback," which occurs under the influence of light of high intensities. 8. Hydroxylamine, applied aerobically, inhibits the adaptation reaction to about the same degree as it inhibits photosynthesis. Photoreduction proceeds after the adaptation in presence of hydroxylamine only at a fraction of the rate that it would have if the poison were added later. 9. Hydroxylamine in concentrations of 10(-3)M protects the anaerobic metabolism against the return to aerobic photosynthesis which normally occurs under the influence of light of too high intensity. The protection is only relative and the higher the light intensity the more hydroxylamine is needed to keep photoreduction going. Once a "turnback" occurs in presence of much hydroxylamine all photochemical gas exchange comes to an end.
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PMID:THE EFFECT OF SPECIFIC POISONS UPON THE PHOTO-REDUCTION WITH HYDROGEN IN GREEN ALGAE. 1987 38

1. Unicellular algae possessing a hydrogenase system (Scenedesmus and other species), and having been adapted by anaerobic incubation to the hydrogen metabolism, reduce oxygen to water according to the equation O(2) + 2H(2) --> 2H(2)O. 2. The oxyhydrogen reaction proceeds undisturbed only in the presence of carbon dioxide, which simultaneously is reduced according to the equation CO(2) + 2H(2) --> H(2)O + (CH(2)O) = (carbohydrate). 3. The maximum yield of the induced reduction is one-half molecule of carbon dioxide reduced for each molecule of oxygen absorbed. 4. Partial reactions are recognizable in the course of the formation of water and it is with the absorption of the second equivalent of hydrogen that the carbon dioxide reduction appears to be coupled. 5. The velocity of the reaction increases in proportion to the partial pressure of oxygen, but only up to a certain point where any excess of oxygen causes the inactivation of the hydrogenase system. The reaction then ends prematurely. 6. During the oxyhydrogen reaction little or no oxygen is consumed for normal respiratory processes. 7. Small concentrations of cyanide, affecting neither photosynthesis nor photoreduction in the same cells, first inhibit the induced reduction of carbon dioxide and then lead to a complete inactivation of the hydrogenase system. 8. Hydroxylamine, added after adaptation, has either no inhibitory effect at all, or prevents solely the induced reduction of carbon dioxide without inactivating the hydrogenase system. 9. Dinitrophenol prevents the dark reduction of carbon dioxide while the reduction of oxygen continues to the formation of water. 10. Glucose diminishes the absorption of hydrogen, probably in its capacity as a competing hydrogen donor. 11. The induced reduction of carbon dioxide can be described as an oxido-reduction similar to that produced photochemically in the same cells.
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PMID:REDUCTION OF CARBON DIOXIDE COUPLED WITH THE OXYHYDROGEN REACTION IN ALGAE. 1987 40