Dehydrogenases of the tricarboxylic acid cycle in Penicillium chrysogenum

Abstract

1. 1. The enzymatic oxidation of succinate, citrate, malate, and lactate has been demonstrated in cell-free extracts obtained from P. chrysogenum Q-176. 2. 2. Succinic dehydrogenase has been isolated by precipitation with (NH 4) 2SO 4 and found to have an optimum pH near 6.6. Malonate, iodoacetate, copper sulfate, and oxalacetate at low concentrations caused the expected inhibition of the succinic dehydrogenase. Citrate and Versene showed marked stimulation when added to the enzyme. 3. 3. A preliminary ethanol or acetone wash was used to demonstrate citrate, malate, and lactate oxidation and the effect of coenzyme addition upon the enzymes involved. It was found that TPN was more effective than DPN as a coenzyme for lactate dehydrogenation and that the addition of flavin adenine dinucleotide had no effect upon the oxidation. 4. 4. Penicillium cells grown upon a synthetic medium, similar to that used for studies of penicillin production, show most of the dehydrogenases requisite for the operation of a tricarboxylic acid cycle except α-ketoglutaric dehydrogenase.