title: alpha-1,4-Glucan lyase performs a trans-elimination via a nucleophilic displacement followed by a syn-elimination.
abstract: alpha-Glucan lyase (EC 4.2.2.13, GLase) cleaves alpha-1,4-glucosidic bonds via an elimination reaction to produce 1,5-d-anhydrofructose. GLase was inactivated by the mechanism based alpha-glucosidase inactivator, 5-fluoro-beta-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 alpha-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.
authors: Department of Chemistry, Protein Engineering Network of Centres of Excellence of Canada, University of British Columbia, Vancouver, BC Canada V6T 1Z1.
authors: Seung Seo
authors: SS
authors: Lee
authors: Shukun
authors: S
authors: Yu
authors: Stephen G
authors: SG
authors: Withers
mesh_terms: D003903:Deuterium; D005947:Glucose / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D005960:Glucosides / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D011133:Polysaccharide-Lyases / Q000737:chemistry / Q000378:metabolism*; D000461:Rhodophyta / Q000201:enzymology; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D005960:Glucosides; C030364:glucosyl fluoride; C019502:4-nitrophenyl alpha-glucoside; D003903:Deuterium; D011133:Polysaccharide-Lyases; C080474:alpha-1,4-glucan lyase; D005947:Glucose