Stereospecific regulation of plant glucan synthetase in vitro

Abstract

Glucan synthesis from uridine diphosphate glucose (UDP-glucose), mediated by particulate-bound enzyme from a variety of plants, is stimulated by a number of sugars and glycols. Glucose and glycerol appear to have a common site of action. Erythritol competitively inhibits glycerol-stimulated glucan synthesis. A marked disparity in stimulation by optical isomers of arabitol is indicative of a stereospecific activator mechanism.At 50 °C, particulate-bound β-1,3-glucanase hydrolyzes most of the glucan previously formed at 22 °C in the presence of glycerol, leaving a resistant glucan residue. Glucan formed in the absence of glycerol was not hydrolyzed.The supernatant above the 12 000 × g particulate fraction contains a heat-stable stimulator, and a heat-labile inhibitor, of glucan synthesis.