2hor
From Proteopedia
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Crystal structure of alliinase from garlic- apo form
Overview
Alliinase (alliin lyase EC 4.4.1.4), a PLP-dependent alpha, beta-eliminating lyase, constitutes one of the major protein components of, garlic (Alliium sativum L.) bulbs. The enzyme is a homodimeric, glycoprotein and catalyzes the conversion of a specific non-protein, sulfur-containing amino acid alliin ((+S)-allyl-L-cysteine sulfoxide) to, allicin (diallyl thiosulfinate, the well known biologically active, component of freshly crushed garlic), pyruvate and ammonia. The enzyme was, crystallized in the presence of (+S)-allyl-L-cysteine, forming, dendrite-like monoclinic crystals. In addition, intentionally produced, apo-enzyme was crystallized in tetragonal form. These structures of, alliinase with associated glycans were resolved to 1.4 A and 1.61 A by, molecular replacement. Branched hexasaccharide chains N-linked to Asn146, and trisaccharide chains N-linked to Asn328 are seen. The structure of, hexasaccharide was found similar to "short chain complex vacuole type", oligosaccharide most commonly seen in plant glycoproteins. An unexpected, state of the enzyme active site has been observed in the present, structure. The electron density in the region of the cofactor made it, possible to identify the cofactor moiety as aminoacrylate intermediate, covalently bound to the PLP cofactor. It was found in the present, structure to be stabilized by large number of interactions with, surrounding protein residues. Moreover, the existence of the expected, internal aldimine bond between the epsilon-amino group of Lys251 and the, aldehyde of the PLP is ruled out on the basis of a distinct separation of, electron density of Lys251. The structure of the active site cavity in the, apo-form is nearly identical to that seen in the holo-form, with two, sulfate ions, an acetate and several water molecules from crystallization, conditions that replace and mimic the PLP cofactor.
About this Structure
2HOR is a Single protein structure of sequence from Allium sativum with NAG, SO4, ACT, CL and NO3 as ligands. Active as Alliin lyase, with EC number 4.4.1.4 Full crystallographic information is available from OCA.
Reference
Two structures of alliinase from Alliium sativum L.: apo form and ternary complex with aminoacrylate reaction intermediate covalently bound to the PLP cofactor., Shimon LJ, Rabinkov A, Shin I, Miron T, Mirelman D, Wilchek M, Frolow F, J Mol Biol. 2007 Feb 16;366(2):611-25. Epub 2006 Nov 14. PMID:17174334
Page seeded by OCA on Wed Nov 21 11:52:39 2007
