Fine structural localization of alkaloid synthesis in endoplasmic reticulum of submergedClaviceps purpurea

Abstract

Acetyl coenzymeA (CoA) carboxylase (EC 6.4.1.2), an enzyme catalyzing the synthesis of malonyl-CoA, was cytochemically localized in endoplasmic reticulum (ER) of sclerotia-like cells of submergedClaviceps purpurea Tul. producing clavine alkaloids. The enzymatic activity was structurally bound in unit membraned of ER strands which, later on, evolved into vacuoled containing lipoprotein material. The reaction product was absent from ER in nonvacuolized filamentous hyphae and ovoid asexual spores containing numerous lipid globules; it was also absent from ER in the mycelium of submergedC. purpurea strain producing no alkaloids. In view of our previous morphogenetic observations and the available biochemical evidence, the observed localization of acetyl-CoA carboxylase was assumed not to coincide with fatty acif biosynthesis but to represent sites of alkaloid synthesis.