UDP-(5F)-GlcNAc acts as a slow-binding inhibitor of MshA, a retaining glycosyltransferase.
Glycosyltransferase enzymes play important roles in numerous cellular pathways. Despite their participation in many therapeutically relevant pathways, there is a paucity of information on how to effectively inhibit this class of enzymes. Here we report that UDP-(5F)-GlcNAc acts as a slow-binding, competitive inhibitor of the retaining glycosyltransferase MshA from Corynebacterium glutamicum (K(i) approximately 1.6 muM). The kinetic data are consistent with a single-step inhibition mechanism whose equilibration is slow relative to catalysis. We believe that this is the first slow-onset inhibitor to be reported for the glycosyltransferase family of enzymes. The potent inhibition of the enzyme by the fluoro-substituted substrate is consistent with the involvement of an oxocarbenium transition-state structure, which has been previously proposed for this family of enzymes. Additionally, although several members of the GT-B enzyme family, including MshA, have been shown to undergo a conformational change upon UDP-GlcNAc binding, the kinetic data are inconsistent with a two-step inhibition mechanism. This suggests that there may be other conformations of the enzyme that are useful for the design of inhibitors against the large family of GT-B glycosyltransferase enzymes.
Frantom
Patrick A
PA
Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA. pfrantom@bama.ua.edu
Coward
James K
JK
Blanchard
John S
JS
D048230:Corynebacterium glutamicum / Q000201:enzymology; D004791:Enzyme Inhibitors / Q000378:metabolism* / Q000494:pharmacology*; D016695:Glycosyltransferases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D007700:Kinetics; D011485:Protein Binding; D014537:Uridine Diphosphate N-Acetylglucosamine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology
D004791:Enzyme Inhibitors; D014537:Uridine Diphosphate N-Acetylglucosamine; C039075:5-fluoro-2'-deoxyuridine diphosphate-N-acetylglucosamine; D016695:Glycosyltransferases
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