Chemical Rescue of α3-Galactosyltransferase. Implications in the Mechanism of Retaining Glycosyltransferases

• Published in: Journal of the American Chemical Society Vol. 128; no. 50; pp. 16030 - 16031
• Main Authors: Monegal, Ana, Planas, Antoni
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 20.12.2006
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Kinetics and mechanisms; Organic chemistry; Reactivity and mechanisms; Reaction mechanism; N-Acetyllactosaminide α-1,3-galactosyltransferase; Hexosyltransferases; Enzyme; Transferases; Glycosyltransferases
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja0659931

The mechanism of retaining glycosyltransferases is still poorly understood and the subject of current debate. Both double displacement and front side single displacement (SNi) mechanisms have been proposed. A “chemical rescue methodology” is here applied to a retaining α3-galactosyltransferase. Azide as exogenous nucleophile rescues the activity of the inactive E317A mutant to give β-d-galactosylazide. This result fits best with a double displacement mechanism in which Glu317 is the enzyme nucleophile involved in the formation of a glycosyl-enzyme intermediate.