Electron acquisition system constructed from an NAD-independent D-lactate dehydrogenase and cytochrome c2 in Rhodopseudomonas palustris No. 7.
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.
Horikiri
Shunsuke
S
Department of Bioresources Science, Graduate School of Science and Technology, Matsudo-shi, Chiba University, Japan.
Aizawa
Yoshiyuki
Y
Kai
Taiki
T
Amachi
Seigo
S
Shinoyama
Hirofumi
H
Fujii
Takaaki
T
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
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