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Publication Abstract from PubMed

l-Rhamnose isomerase (l-RhI) catalyzes the reversible isomerization of l-rhamnose to l-rhamnulose. Previously determined X-ray structures of l-RhI showed a hydride-shift mechanism for the isomerization of substrates in a linear form, but the mechanism for opening of the sugar-ring is still unclear. To elucidate this mechanism, we determined X-ray structures of a mutant l-RhI in complex with l-rhamnopyranose and d-allopyranose. Results suggest that a catalytic water molecule, which acts as an acid/base catalyst in the isomerization reaction, is likely to be involved in pyranose-ring opening, and that a newly found substrate sub-binding site in the vicinity of the catalytic site may recognize different anomers of substrates.

Structure of l-rhamnose isomerase in complex with l-rhamnopyranose demonstrates the sugar-ring opening mechanism and the role of a substrate sub-binding site.,Yoshida H, Yoshihara A, Teraoka M, Yamashita S, Izumori K, Kamitori S FEBS Open Bio. 2012 Dec 7;3:35-40. doi: 10.1016/j.fob.2012.11.008. Print 2013. PMID:23772372^[1]

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