alpha-1,4-Glucan lyase performs a trans-elimination via a nucleophilic displacement followed by a syn-elimination.
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.
Lee
Seung Seo
SS
Department of Chemistry, Protein Engineering Network of Centres of Excellence of Canada, University of British Columbia, Vancouver, BC Canada V6T 1Z1.
Yu
Shukun
S
Withers
Stephen G
SG
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
D005960:Glucosides; C030364:glucosyl fluoride; C019502:4-nitrophenyl alpha-glucoside; D003903:Deuterium; D011133:Polysaccharide-Lyases; C080474:alpha-1,4-glucan lyase; D005947:Glucose