Interaction of Cytochrome c with Yeast D(—) Lactic Oxidase

Abstract

IN 1961 Gregolin and Singer¹ reported that yeast respiratory particles, prepared by mechanical disruption of cells in 1 per cent NaCl, do not oxidize D( — ) laetate with oxygen as the terminal electron acceptor. However, the particles exhibit strong D( — ) lactic dehydrogenase activity, and oxidize D( — ) laetate with oxygen uptake on addition of external cytochrome c. More recently, Gregolin and D'Alberton observed² that D( — ) laetate is oxidized at high rate by oxygen when respiratory particles are prepared by disintegration of the cells in sucrose solution. When tested in a medium known to give maximal oxidase activity, the oxidation is not stimulated by addition of cytochrome c. In the presence of the same mixture (plus NaN₃), D( — ) lactate is not oxidized by this preparation with cytochrome c as artificial electron acceptor.