@Copyright 1991 by The Humana Press Inc. All rights of any nature whatsoever reserved. 0273--2289/91/3103--0237502.60 Inhibition of Dextransucrase by C -D-Glucose Derivatives ALAN G. MICHIELS, ALBERT Y. WANG, DOUGLAS S. CLARK, AND HARVEY W. BLANCH* Department of Chemical Engineering, University of California, Berkeley, CA 94 720 Received January 7, 1991; Accepted June 25, 1991 ABSTRACT r fluoride was modified at positions 2, 3, or 5 and these analogs were tested as substrates and inhibitors of dextran- sucrase from Leuconostocmesenteroides B-512F. The analogs studied were 2-deoxy-2-fluoro~-D-glucopyranosyl fluoride, 3-deoxy-3-fluoro- o~-D-glucopyranosyl fluoride, 3-deoxy-3-thio-o~-D-glucopyranosyl fluoride, and 5-thio~-D-glucopyranosyl fluoride. Kinetic constants for cx-D-glucopyranosyl fluoride were also determined. None of the cx-D-glucopyranosyl fluorides were accepted as sub- strates for dextransucrase. 2-Deoxy-2-fluoro-cx-D-g!ucopyranosyl fluoride, 3-deoxy-3-fgluoro-~-D-glucopyranosyl fluoride, and 3-deoxy- 3-thio-~-D-glucopyranosyl fluoride were competitive inhibitors with /~ values of 63, 93, and 53 mM, respectively. The Km for cx-D-gluco- pyranosyl fluoride was found to be 26 mM. The data indicate that the hydroxyl groups at C2 and C3 are important for proper binding of a-D-glucopyranosyl fluoride for the active site of dextransucrase and that the C3-hydroxyl probably acts as a hydrogen-bond donor. Index Entries: Dextransucrase; c~-D-glucopyranosyl fluoride; dextran; Leuconostoc mesenteroides; inhibition. INTRODUCTION Dextransucrases from several species and strains of Leuconostoc and Streptococcus utilize sucrose as an c~-D-glucosyl donor for the synthesis of *Author to whom all correspondence and reprint requests should be addressed. Applied Biochemistry and Biotechnology 23 7 VoL 3 I, 1991