Bacterial α-glucan phosphorylases

Abstract

Although glycogen and other alpha-1,4-D-glucan storage polysaccharidesare present in many bacteria, only few glucan phosphorylases frombacteria have been identified and characterised on the protein or genelevel. All bacterial phosphorylases follow the same catalytic mechanismsas their plant and vertebrate counterparts, but differ considerably interms of their substrate specificity and regulation. The catalyticdomains are highly conserved while the regulatory sites are only poorlyconserved. The degree of conservation between bacterial and mammalianphosphorylases is comparable to that of other nonmammalian and mammalianalpha-glucan phosphorylases. Only for maltodextrin phosphorylase from E:coli the physiological role of the enzyme in the utilisation ofmaltodextrins is known in detail; that of all other phosphorylasesremains still unclear. Roles in regulation of endogenous glycogenmetabolism in periods of starvation, and sporulation, stress response orquick adaptation to changing environments are imaginable. (C) 1999Federation of European Microbiological Societies. Published by ElsevierScience B.V. All rights reserved.