Inhibition of Catalytic and Glucan-Binding Activities of a Streptococcal GTF Forming Insoluble Glucans

Abstract

The ability of a range of potential inhibitors to affect the catalytic activity or binding of dextran by a glucosyltransferase (GTF-I) that synthesises insoluble α1,3-linked glucan was tested. Acarbose, deoxynojirimycin, N-dodecyldeoxynojirimycin and Tris, which are thought to interfere with the active site of the enzyme of GTF and related glycosidases, inhibited glucan synthesis but not glucan binding. Tris was found to act as a competitive inhibitor of GTF-I. The effectiveness of the active site inhibitors was not altered by immobilisation of GTF-I on saliva-coated hydroxyapatite. In contrast, three amine hydrofluorides were markedly less effective against immobilised GTF than soluble GTF. The pH of the reaction mixture was found to have a strong influence on inhibition by acarbose, Tris and amine hydrofluorides, a finding that is of direct relevance to use of inhibitors in vivo.