Comparative Studies of Glyoxysomes from Various Fatty Seedlings

The separation of various organelles from cotton cotyledon (Gossypium hirsutum L.), cucumber cotyledon (Cucumis sativus L.), peanut cotyledon (Archis hypogaea L.), pine megagametophyte (Pinus ponderosa Laws), and watermelon cotyledon (Citrullus vulgaris Schrad.) by sucrose density gradient centrifugation was found to be similar to that described for castor bean endosperm (Ricinus communis L.). Equilibrium densities were 1.12 to 1.13 g cm(3) for endoplasmic reticulum, 1.17 to 1.19 g/cm(3) for mitochondria, and 1.25 g/cm(3) for glyoxysomes. Isolated glyoxysomes from different fatty seedlings have striking similar specific activities of individual enzymes. The only exception is alkaline lipase activity which, when assayed with an artificial substrate, varies some 10-fold in glyoxysomes from different fatty seedlings. The properties of individual enzymes in glyoxysomes from different fatty seedlings are qualitatively similar as regard to sub-organelle localization and behavior in the presence of KCl and Triton X-100. In pine megagametophyte, the glyoxysomes and not the mitochondria are the intracellular site for the breakdown of stored lipid.