Bacterial alpha-glucan phosphorylases

Although glycogen and other alpha-1,4-D-glucan storage polysaccharides are present in many bacteria, only few glucan phosphorylases from bacteria have been identified and characterised on the protein or gene level. All bacter ial phosphorylases follow the same catalytic mechanisms as their plant and vertebrate counterparts, but differ considerably in terms of their substrat e specificity and regulation. The catalytic domains are highly conserved wh ile the regulatory sites are only poorly conserved. The degree of conservat ion between bacterial and mammalian phosphorylases is comparable to that of other nonmammalian and mammalian alpha-glucan phosphorylases. Only for mal todextrin phosphorylase from E: coli the physiological role of the enzyme i n the utilisation of maltodextrins is known in detail; that of all other ph osphorylases remains still unclear. Roles in regulation of endogenous glyco gen metabolism in periods of starvation, and sporulation, stress response o r quick adaptation to changing environments are imaginable. (C) 1999 Federa tion of European Microbiological Societies. Published by Elsevier Science B .V. All rights reserved.