Evidence for De Novo Synthesis of Isocitratase and Malate Synthesis in Germinating Peanut Cotyledons

Evidence for de novo synthesis of isocitratase and malate synthetase in cotyledons of germinating peanut (Arachis hypogaea L.) was obtained by the density labeling method. When dry peanut cotyledons were cultured in H(2) (18)O, a 2.4% increase in the buoyant density of malate synthetase in a cesium chloride gradient was observed. In 100% D(2)O the buoyant density shift was 5.5% for isocitratase and 3.5% for malate synthetase in comparison to the water controls. These data suggest that isocitratase and malate synthetase do not pre-exist in some inactive form in the cotyledons, but are completely synthesized after onset of germination from a pool of amino acids which do not derive directly from hydrolysis of storage proteins.