Cytochrome c modified by digestion with proteolytic enzymes: 2. Properties of pepsin-modified cytochrome c

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Abstract
Fe, total N, total amino-N and alpha-amino N contents of cytochrome c modified by pepsin were detd. and the amino acids present identified. The adsorption spectra of the oxidized and reduced forms of this pigment resembled closely those of ordinary cytochrome c. This pigment combined with cyanide, meth-ylcarbylamine, CO2, nitric oxide and nitrosobenzene. It was autoxidizable and showed properties similar to type V of ordinary cytochrome c (i. e., cytochrome c at pH 13) on the one hand and hemoglobin on the other. It was inactive in both the succinic oxi-dase system and the cytochrome oxidase system with p-phenylene-diamine as substrate, but strongly catalyzed the oxidation of ascorbic acid. As an artificial ascorbic acid oxidase, it had a QO2 of 11,500. This catalyzed oxidation of ascorbic acid was inhibited by cyanide, methylcarbylamine, nitrosobenzene and CO, the latter inhibition being somewhat light-sensitive. The pigment showed little catalatic activity and was devoid of peroxidatic activity.