BIOGENESIS OF MITOCHONDRIA .9. FORMATION OF SOLUBLE MITOCHONDRIAL ENZYMES MALATE DEHYDROGENASE AND FUMARASE IN SACCHAROMYCES CEREVISIAE

Adaptive changes in the composition and number of mitochondria formed in Saccharomyces cerevisiae were brought about by growing the organism under conditions of glucose repression, or in anaerobic conditions, or in the presence of chloramphenicol. Glucose repressed the formation of malate dehydrogenase in both cytoplasmic and mitochondrial compartments of the cell; fumarase formation was repressed only in the mitochondrial fraction. The effect of chloramphenicol depended on the extent of repression, but the synthesis of both enzymes and their incorporation into the mitochondrial fraction was at most partly affected. Furthermore, the oxygen-induced formation of these enzymes in nongrowing cells was found to be insensitive to chloramphenicol. This was also true for the particulate enzyme succinate dehydrogenase. It is concluded that these proteins are not products of the mitochondrial protein synthesizing system. The formation of cytochrome oxidase was completely inhibited by chloramphenicol. Cycloheximide blocked the induction of all enzymes measured. The isoenzymes of malate dehydrogenase reported to be present in this yeast could not be detected in the particular strain used in these experiments. It is suggested that single forms of malate dehydrogenase and fumarase are synthesized in the cytoplasm of these cells for both cytoplasmic and mitochondrial functions. © 1969.