The succinic oxidase and DPNH oxidase systems of the bay mussel, Mytilus edulis

Abstract

Respiratory particles have been prepared from adductor muscles of four lamellibranch mollusks. Nearly a tenfold increase in specific activity for succinic oxidase has been obtained. The respiratory particles of posterior adductor muscles of bay mussel, Mytilus edulis, have been studied in more detail. They can catalyze the oxidation of succinate, malate and reduced diphosphopyridine nucleotide (DPNH) by molecular oxygen and by mammalian cytochrome c. The rate of succinate oxidation by oxygen is stimulated by exogenous cytochrome c and inhibited by antimycin A or cyanide. The rate of DPNH oxidation by oxygen is slightly inhibited by the addition of amytal, antimycin, or cyanide and greatly increased by cytochrome c. In the presence of cytochrome c, DPNH oxidation is potently inhibited by cyanide. The existence of cytochrome oxidase in mussel particles is demonstrated by their capability to oxidize ascorbate and reduced cytochrome c. The convergence of the succinate and the DPNH respiratory chains is demonstrated from the simultaneous oxidations of these substrates; rates of these oxidations are not additive. The existence of absorption bands similar to cytochromes c-c 1, b, and a-a 3 of sarcosomal components has been shown by direct spectroscopic examination of mussel particles.