The lactic dehydrogenase of Penicillium chrysogenum.

A soluble, cytochrome linked flavoprotein which oxidizes lactic acid to pyruvic acid has been isolated from Penicillium chrysogenum, strain NRRL 1951 -B25. The reduction of cytochrome c by a flavin enzyme has precedence in the work of Horecker and Heppel (1949) and Mlorell (1952) who have shown that xanthine oxidase can reduce cytochrome c. Morell reported the enzyme to be inhibited strongly by phosphate buffers; this agrees with a phosphate inhibition of the lactic dehydrogenase of P. chrysogenum when flavin-adenine dinucleotide is the coenzyme. A cytochrome linked lactic dehydrogenase from Delft Baker's yeast has been reported by Bernheim (1928); this enzyme was solubilized by Ogston and Green (1935) and purified to a dry stable preparation by Gurchot and Lowman (1936). Ogston and Green compared various electron carriers and concluded that methylene blue and cytochrome c allowed the best oxidation of lactic acid by the enzyme. Later reports by Bach et al. (1942, 1946) show that even with highly purified preparations cytochrome c or methylene blue was the only addition needed for maximum activity although there was some indication that an additional factor was necessary for the system to react with cytochrome c. This paper describes a soluble cytochrome linked lactic dehydrogenase from P. chrysogenum, strain NRRL 1951 *B25.