Sucrose Density Gradient Distribution of Mitochondrial Protein and Enzymes from Preclimacteric and Climacteric Pears

Abstract

Mitochondrial fractions isolated from pears (Pyrus communis L.) at the climacteric minimum and peak were subjected to sucrose density gradient centrifugation. The distribution of protein and specific activities of 3 enzymes from this mitochondrial fraction were investigated. Cytochrome oxidase specific activity remained associated with the particulate fraction and increased slightly during the period in which respiration of the whole fruit reached its climacteric peak. Catalase and acid phosphatase specific activity was associated with both the particulate and the least dense region of the gradient and decreased with postharvest ripening. Evidence for several differences between the subcellular behavior of catalase and acid phosphatase from pear tissue compared to their counterparts isolated from mammalian cells is discussed. A general shift of maximum specific enzymic activities and protein distribution to lighter regions of the density gradient occurs with ripening, suggestive of diminution in size or density of intracellular particles.