| 5732503 |
Jurtshuk P, Harper L: Oxidation of D (minus) lactate by the electron transport fraction of Azotobacter vinelandii. J Bacteriol. 1968 Sep;96(3):678-86.
d (-) Lactate oxidation in Azobacter vinelandii strain O is readily carried out by the membrane bound enzyme that concentrates in the electron transport fraction (R (3)). This oxidation in the R (3) fraction is not dependent on externally added nicotinamide adenine dinucleotide, flavine adenine dinucleotide, or flavine mononucleotide. Phenazine methosulfate, O (2), and menadione all served as good electron carriers, and the oxidation of lactate was limited to the d (-) stereoisomer. Of all the alpha-hydroxyacids examined, only d (-) lactate and d (-) alpha-hydroxybutyrate were oxidized by the R (3) fraction. Paper chromatographic studies revealed that the 2,4-dinitrophenylhydrazine derivative formed from d (-) lactate oxidation was pyruvate. Pyruvate, in turn, could be further decarboxylated nonoxidatively by the R (3) fraction. Spectral studies revealed that both the R (3) flavoprotein and cytochrome (a (2), a (1), b (1), c (4), and c (5)) components were reduced by d (-) lactate. The d (-) lactic oxidase activity was sensitive to electron transport inhibitors, i.e., chlorpromazine, antimycin A, 2-n-heptyl-4-hydroxyquinoline-N-oxide, rotenone, dicumarol, and cyanide, and to a small extent to 4,4,4-trifluoro-1-(2-thienyl)-1,3-butane-dione (TFTB) and Amytal. The d (-) lactic phenazine methosulfate and menadione reductases were sensitive only to dicumarol and TFTB. Chlorpromazine was found to be a highly specific inhibitor of d (-) lactic oxidase activity, 50% inhibition occurring at 6.6 x 10 (-6) m. |
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