Document Type

Article

Publication Date

9-8-2008

Journal or Book Title

Carbohydrate Research

Volume

343

Issue

13

First Page

2235

Last Page

2242

DOI

10.1016/j.carres.2008.05.026

Abstract

It has been difficult to identify the proton donor and nucleophilic assistant/base of endoplasmic reticulum α-(1→2)-mannosidase I, a member of glycoside hydrolase Family 47, which cleaves the glycosidic bond between two α-(1→2)-linked mannosyl residues by the inverting mechanism, trimming Man9GlcNAc2 to Man8GlcNAc2 isomer B. Part of the difficulty is caused by the enzyme’s use of a water molecule to transmit the proton that attacks the glycosidic oxygen atom. We earlier used automated docking to conclusively determine that Glu435 in the yeast enzyme (Glu599 in the corresponding human enzyme) is the nucleophilic assistant. The commonly accepted proton donor has been Glu330 in the human enzyme (Glu132 in the yeast enzyme). However, for theoretical reasons this conclusion is untenable. Theory, automated docking of α-d-3S1-mannopyranosyl-(1→2)-α-d-4C1-mannopyranose and water molecules associated with candidate proton donors, and estimation of dissociation constants of the latter have shown that the true proton donor is Asp463 in the human enzyme (Asp275 in the yeast enzyme).

Comments

This is a post-print of an article from Carbohydrate Research, 343, no. 13 (8 September 2008): 2235–2242, doi: 10.1016/j.carres.2008.05.026.

Copyright Owner

Elsevier Ltd.

Language

en

File Format

application/pdf

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