1obb

From Proteopedia

Revision as of 15:09, 18 December 2007

ALPHA-GLUCOSIDASE A, AGLA, FROM THERMOTOGA MARITIMA IN COMPLEX WITH MALTOSE AND NAD+

Overview

Glycoside hydrolase family 4 represents an unusual group of glucosidases, with a requirement for NAD+, divalent metal cations, and reducing, conditions. The family is also unique in its inclusion of both alpha- and, beta-specific enzymes. The alpha-glucosidase A, AglA, from Thermotoga, maritima is a typical glycoside hydrolase family 4 enzyme, requiring NAD+, and Mn2+ as well as strongly reducing conditions for activity. Here we, present the crystal structure of the protein complexed with NAD+ and, maltose, refined at a resolution of 1.9 A. The NAD+ is bound to a typical, Rossman fold NAD+-binding site, and the nicotinamide moiety is localized, close to the maltose substrate. Within the active site the conserved, Cys-174 and surrounding histidines are positioned to play a role in the, hydrolysis reaction. The electron density maps indicate that Cys-174 is, oxidized to a sulfinic acid. Most likely, the strongly reducing conditions, are necessary to reduce the oxidized cysteine side chain. Notably, the, canonical set of catalytic acidic residues common to other glucosidases is, not present in the active site. This, combined with a high structural, homology to NAD-dependent dehydrogenases, suggests an unusual and possibly, unique mechanism of action for a glycoside-hydrolyzing enzyme.

About this Structure

1OBB is a Single protein structure of sequence from Thermotoga maritima with MAL and NAD as ligands. Active as Alpha-glucosidase, with EC number 3.2.1.20 Known structural/functional Site: . Full crystallographic information is available from OCA.

Reference

Crystal structure of Thermotoga maritima alpha-glucosidase AglA defines a new clan of NAD+-dependent glycosidases., Lodge JA, Maier T, Liebl W, Hoffmann V, Strater N, J Biol Chem. 2003 May 23;278(21):19151-8. Epub 2003 Feb 14. PMID:12588867

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