title: Electron acquisition system constructed from an NAD-independent D-lactate dehydrogenase and cytochrome c2 in Rhodopseudomonas palustris No. 7.
abstract: The activities of NAD-independent D- and L-lactate dehydrogenases (D-LDH, L-LDH) were detected in Rhodopseudomonas palustris No. 7 grown photoanaerobically on lactate. One of these enzymes, D-LDH, was purified as an electrophoretically homogeneous protein (M(r), about 235,000; subunit M(r) about 57,000). The pI was 5.0. The optimum pH and temperature of the enzyme were pH 8.5 and 50 degrees C, respectively. The Km of the enzyme for D-lactate was 0.8 mM. The enzyme had narrow substrate specificity (D-lactate and DL-2-hydroxybutyrate). The enzymatic activity was competitively inhibited by oxalate (Ki, 0.12 mM). The enzyme contained a FAD cofactor. Cytochrome c(2) was purified from strain No. 7 as an electrophoretically homogeneous protein. Its pI was 9.4. Cytochrome c(2) was reduced by incubating with D-LDH and D-lactate.
authors.affiliation: Department of Bioresources Science, Graduate School of Science and Technology, Matsudo-shi, Chiba University, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Horikiri
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Aizawa
authors.forename: Taiki
authors.initials: T
authors.lastname: Kai
authors.forename: Seigo
authors.initials: S
authors.lastname: Amachi
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Shinoyama
authors.forename: Takaaki
authors.initials: T
authors.lastname: Fujii
mesh_terms: D003067:Coenzymes / Q000032:analysis; D045362:Cytochromes c2 / Q000737:chemistry* / Q000302:isolation & purification; D004579:Electron Transport; D004789:Enzyme Activation; D005486:Flavin Mononucleotide / Q000032:analysis; D005182:Flavin-Adenine Dinucleotide / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D007770:L-Lactate Dehydrogenase / Q000737:chemistry / Q000302:isolation & purification; D045022:Lactate Dehydrogenases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D019344:Lactic Acid / Q000378:metabolism; D012241:Rhodopseudomonas / Q000201:enzymology*; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D003067:Coenzymes; D005182:Flavin-Adenine Dinucleotide; D019344:Lactic Acid; D005486:Flavin Mononucleotide; D045362:Cytochromes c2; D045022:Lactate Dehydrogenases; D007770:L-Lactate Dehydrogenase; C071195:D-lactate dehydrogenase