Abstract
1. 1. Extracts of Moraxella lwoffi and Escherichia coli were found to contain high levels of diaphorase activity with NADH or NADPH as electron donor and DCIP or ferricyanide as electron acceptor. 2. 2. With M. lwoffi extracts lipoamide could replace the artificial acceptors with NADH but not NADPH as electron donor. No such activity was found with E. coli extracts. 3. 3. The reversibility of the reaction catalysed by lipoamide dehydrogenase (NADH: lipoamide oxidoreductase, EC 1.6.4.3) was studied in extracts of 12 different species of bacteria. 4. 4. The results suggested that there may be a correlation between the fermentative capacity of the organism and the sensitivity of its lipoamide dehydrogenase to inhibition by NADH. 5. 5. NAD-linked lactate dehydrogenase ( l-lactate:NAD oxidoreductase, EC 1.1.2.3) was present in high levels in extracts of fermenting organisms but weakly active in or entirely absent from those of non-fermenting organisms. 6. 6. It is suggested that both enzymes may be involved in the metabolic control processes which govern the capacity of an organism to adapt to changes in the oxygen tension of its environment.
Published Version
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