Subcellular fractionation by zonal centrifugation of glucose-repressed anaerobically grown Saccharomyces carlsbergensis.

1. Homogenates were prepared from sphaeroplasts of anaerobically grown, glucoserepressed Saccharomyces carlsbergensis, and the distributions of marker enzymes investigated after zonal centrifugation on sucrose gradients containing 2mm-MgCl(2). 2. These homogenates contained no detectable cytochrome c oxidase, succinate-cytochrome c oxidoreductase, succinate-ferricyanide oxidoreductase, l(+)-lactate-cytochrome c oxidoreductase or catalase. Cytochromes a+a(3) and c were not detected. 3. Zonal centrifugation of whole homogenates indicated complex density distributions of the sedimentable portions of NADH- and NADPH-cytochrome c oxidoreductases, adenosine triphosphatases (ATPases), adenosine pyrophosphatase (ADPase), pyrophosphatase and acid p-nitrophenyl phosphatase. Several different ATPases were distinguished on the basis of their sensitivities to oligomycin and ouabain. 4. Differential centrifugation of whole homogenates at 10(5)g-min left 80-90% of the protein, dithionite-reducible cytochrome b, acid hydrolases and pyrophosphatase in a supernatant (S(1)) together with 65 and 56% of the NADH- and NADPH-cytochrome c oxidoreductases respectively, 25% of the ATPases and 71% of the adenosine monophosphatase. 5. Further analysis of supernatant S(1) revealed the presence of a class of small particles containing NADPH-cytochrome c oxidoreductases and ATPases. 6. At least four different populations of large particles were distinguished. 7. Electron microscopy indicated that one of these corresponded to ;promitochondria' as described by other workers.