TRIPHOSPHOPYRIDINE NUCLEOTIDE - CYTOCHROME c REDUCTASE IN LIVER

In yeast the reduction of ferricytochrome c by reduced triphosphopyridine nucleotide (TPNH2) is catalyzed by a flavoprotein, cytochrome c reductase, which contains flavin mononucleotide (FMN, riboflavin phosphate) as the prosthetic group (1). In animal tissue the reduction of ferricytochrome c by TPNHz has not yet been reported, although the reaction with reduced diphosphopyridine nucleotide (DPNH2) has been observed with pig heart suspensions (2) and liver extracts (3). TPN-cytochrome c reductase has now been isolated from pig liver’ and identified as a flavoprotein with flavin-adenine dinucleotide (FAD) as the prosthetic group. The specific activity of the purified enzyme is the same as that of yeast eytochrome c reductase. In the present report the details of the isolation procedure and the properties of the purified liver enzyme are described.