α-1,4-glucan lyase performs a trans-elimination via a nucleophilic displacement followed by a syn-elimination

Lee, Seung Seo, Yu, Shukun and Withers, Stephen G. (2002) α-1,4-glucan lyase performs a trans-elimination via a nucleophilic displacement followed by a syn-elimination. Journal of the American Chemical Society, 124 (18), 4948-4949. (doi:10.1021/ja0255610).

Record type: Article

Abstract

?-Glucan lyase (EC 4.2.2.13, GLase) cleaves ?-1,4-glucosidic bonds via an elimination reaction to produce 1,5-d-anhydrofructose. GLase was inactivated by the mechanism based ?-glucosidase inactivator, 5-fluoro-?-l-idosyl fluoride. The trapped glycosyl-enzyme intermediate was isolated and the nucleophilic amino acid residue (Asp 553) identified is equivalent to the residue so identified in sequence-related ?-glucosidases. This intermediate undergoes a syn-elimination reaction to release the product. Further evidence against a direct trans-elimination mechanism was provided by the absence of a primary kinetic isotope effect on the substrate substituted with deuterium at the C2 position.

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