The reduction of cytochrome c by xanthine oxidase and the competitive inhibition of this
process by carbonic anhydrase and by myoglobin have been studied by kinetic and by
equilibrium binding methods. Carbonic anhydrases isolated from bovine and from human
erythrocytes differed strikingly in their ability to inhibit competitively the reduction of
cytochrome c. The K s for cytochrome c was a function of the concentration of xanthine
oxidase, as were K i for carbonic anhydrase and K i for myoglobin, whereas K s for xanthine …