title: 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.
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.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Georgia, Athens, USA.
authors.forename: L
authors.initials: L
authors.lastname: Chen
authors.forename: J
authors.initials: J
authors.lastname: LeGall
authors.forename: P
authors.initials: P
authors.lastname: Fareleira
authors.forename: H
authors.initials: H
authors.lastname: Santos
authors.forename: A V
authors.initials: AV
authors.lastname: Xavier