Respiratory Adaptation of Anaerobically Grown Saccharomyces uvarum: Changes in Distribution of Enzymes

Abstract

Subcellular fractionations using metrizamide density gradients revealed intermediary stages of respiratory adaptation of Saccharomyces uvarum grown anaerobically in the presence of the density label 16-bromo-9-hexadecenoic acid. Prior to adaptation, activities of malate dehydrogenase and oligomycin-sensitive ATPase were contained within a membrane population at ρ = 1·20 g ml−1. After 10 min adaptation cytochrome c oxidase activity was associated with these membranes, with ATPase-containing membranes at lower densities (ρ = 1·05 to 1·14 g ml−1) and with membranes containing malate dehydrogenase at higher density (ρ = 1·24 g ml−1). After further adaptation these enzymes were associated firstly with two distinct membrane populations at ρ = 1·17 and 1·20 g ml−1 and finally with a single population of mitochondria at ρ = 1·16 g ml−1. The significance of these changes is discussed in terms of mitochondrial differentiation. Peroxisomes were evident even in early stages of respiratory adaptation and were well separated from mitochondria in later stages.