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1983
Journal Article
Titel
Kinetics and electron transport of soil hydrogenases catalyzing the oxidation of atmospheric hydrogen
Abstract
The soil hydrogenases of chernozem and eolian sand were different with respect to their kinetic properties. Increase of soil moisture above optimum content or prior incubation of the soils under very high H2-mixing ratios (i.e. 1%) resulted in a decrease of V sub max or in an increase of the K sub m of the H2 oxidation reaction. Under anaerobic conditions, the K sub m for H2 was higher and V sub max was lower than under aerobic conditions. The anaerobic H2-oxidation activity of both soils was stimulated by the addition of artificial electron acceptors with redox potentials of at least 80 mV. Ferricyanide as the most efficient stimulator did not function as a final electron acceptor for anaerobic H2-oxidation, but acted as a catalyst by bypassing a rate-limiting electron transport step. In eolian sand, the aerobic as well as the anaerobic activity for atmospheric H2 oxidation decreased upon exposure to very high H2-mixing ratios (i.e. 1%). A similar effect was observed after incubation with ferricyanide which enabled the inflow of excess electrons from soil reductants or added NADH into the electron transport system of the soil hydrogenase with anaerobic activity. The activity for atmospheric H2-oxidation was regenerated during incubation in H2-free atmospheres, especially in the presence of oxygen. Inhibition and regeneration were probably due to alterations in components of the soil hydrogenases caused by the extent of a maximal electron flow through the electron transport system of the soil hydrogenases. (IFU)