Malate metabolism by Desulfovibrio gigas and its link to sulfate and fumarate reduction: purification of the malic enzyme and detection of NAD(P)+ transhydrogenase activity |
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Authors: | Chen L LeGall J Fareleira P Santos H Xavier A V |
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Affiliation: | Department of Biochemistry and Molecular Biology, University of Georgia, Athens, USA. |
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Abstract: | Malate metabolism was investigated in lactate grown cells of Desulfovibrio gigas ; 3 mol of malate are converted into 2 mol succinate and 1 mol acetate. The malic enzyme (L-malate:NADP+ oxidoreductase) was purified to homogeneity and partially characterized. The enzyme is monomeric with molecular weight of 45 kDa. Its spectrum has no visible absorption and the activity is stimulated by K+ and Mg2+. The presence of an NAD(P)+ transhydrogenase, the observation of partial reduction of adenylylsulfate reductase by NADH (via NADH-rubredoxin oxidoreductase) and evidence for NADH-linked fumarate reductase activity support the involvement of pyridine nucleotides in the electron pathway toward the reduction of sulfur compounds and/or fumarate. An electron transfer chain to fumarate is proposed, taking into consideration these results and the stoichiometry of end-products derived from malate dismutation. |
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