2vun

Publication Abstract from PubMed

The hydrolysis of 1,4,5,6-tetrahydro-6-oxonicotinate to 2-formylglutarate is a central step in the catabolism of nicotinate in several Clostridia and Proteobacteria. This reaction is catalyzed by the novel enzyme enamidase, a new member of the amidohydrolase superfamily as indicated by its unique reaction, sequence relationship, and the stoichiometric binding of iron and zinc. A hallmark of enamidase is its capability to catalyze a two-step reaction: the initial decyclization of 1,4,5,6-tetrahydro-6-oxonicotinate leading to 2-(enamine)glutarate followed by an additional hydrolysis step yielding (S)-2-formylglutarate. Here, we present the crystal structure of enamidase from Eubacterium barkeri at 1.9 A resolution, providing a structural basis for catalysis and suggesting a mechanism for its exceptional activity and enantioselectivity. The enzyme forms a 222-symmetric tetramer built up by a dimer of dimers. Each enamidase monomer consists of a composite beta-sandwich domain and an (alpha/beta)(8)-TIM-barrel domain harboring the active site. With its catalytic binuclear metal center comprising both zinc and iron ions, enamidase represents a special case of subtype II amidohydrolases.

The crystal structure of enamidase: a bifunctional enzyme of the nicotinate catabolism.,Kress D, Alhapel A, Pierik AJ, Essen LO J Mol Biol. 2008 Dec 26;384(4):837-47. Epub 2008 Sep 12. PMID:18805424^[3]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.