Identification of enzymically inactive apocytochrome c peroxidase in anaerobically grown Saccharomyces cerevisiae.

Anaerobically grown yeast cells lack cytochrome c peroxidase activity but rapidly acquire it upon aeration. In order to study the oxygen-induced formation of this hemoprotein, extracts of anaerobic and aerobic yeast cells were resolved by one- and two-dimensional acrylamide gel electrophoresis and the separated polypeptides were then checked for comigration with radiolabeled purified cytochrome c peroxidase from aerobic cells or for reaction with cytochrome c peroxidase antiserum. Both types of extracts contained roughly equal amounts of a polypeptide which was indistinguishable from apocytochrome c peroxidase with respect to antigenicity, isoelectric point, and apparent molecular weight in three different gel systems. In confirmation of an earlier report by Sels. A.A., and Cocriamont, C. (1968) (Biochem. Biophus. Res. Commun. 32, 192-198) the oxygen-induced formation of cytochrome c peroxidase was insensitive to inhibitors of protein synthesis and could be mimicked by the addition of heme to extracts of anaerobic cells. We conclude that the oxygen-induced formation of yeast cytochrome c peroxidase involves the addition of heme to the apoenzyme which is already present in the anaerobically grown cells.