Enzymes of glycerol metabolism in the storage tissues of Fatty seedlings

Abstract

Various enzymes of glycerol metabolism in the extracts of 5-day-old eastor bean (Ricinus communis L. var. Hale) endosperm and 4-day-old peanut (Archis hypogaea L.) cotyledon were studied. NAD-glycerol dehydrogenase and NAD-alpha-glycerolphosphate dehydrogenase were not detected. Glycerol kinase was detected in the soluble fractions and an alpha-glycerolphosphate oxidoreductase was found in the particulate fractions. The particulate fractions were separated into various organelle fractions by sucrose gradient centrifugation and the alpha-glycerolphosphate oxidoreductase was shown to be present in the mitochondria. The properties of the castor bean mitochondrial alpha-glycerolphosphate oxidoreductase resembled those of a similar enzyme present in the mitochondria of many animal tissues. A survey showed that the alpha-glycerolphosphate oxidoreductase was present in great amount only in the storage tissues of fatty seedlings but not in other nonfatty plant tissues. It is concluded that in the storage tissues of fatty seedlings, the soluble glycerol kinase and the mitochondrial cytochrome-linked alpha-glycerolphosphate oxidoreductase are the two enzymes responsible for the initial conversion of glycerol to hexose.