Structure of a Novel Enzyme That Catalyzes Acyl Transfer to Alcohols in Aqueous Conditions

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• 作者：Irimpan Mathews ; Michael Soltis ; Mae Saldajeno ; Grant Ganshaw ; Rafael Sala ; Walter Weyler ; Marguerite A. Cervin ; Gregg Whited ; Richard Bott
• 刊名：Biochemistry
• 出版年：2007
• 出版时间：August 7, 2007
• 年：2007
• 卷：46
• 期：31
• 页码：8969 - 8979
• 全文大小：861K
• 年卷期：v.46,no.31(August 7, 2007)
• ISSN：1520-4995

文摘

The unusual architecture of the enzyme (MsAcT) isolated from Mycobacterium smegmatisforms the mechanistic basis for favoring alcoholysis over hydrolysis in water. Unlike hydrolases thatperform alcoholysis only under anhydrous conditions, MsAcT demonstrates alcoholysis in substantiallyaqueous media and, in the presence of hydrogen peroxide, has a perhydrolysis:hydrolysis ratio 50-foldgreater than that of the best lipase tested. The crystal structures of the apoenzyme and an inhibitor-boundform have been determined to 1.5 Å resolution. MsAcT is an octamer in the asymmetric unit and formsa tightly associated aggregate in solution. Relative to other structurally similar monomers, MsAcT containsseveral insertions that contribute to the oligomerization and greatly restrict the shape of the active site,thereby limiting its accessibility. These properties create an environment by which MsAcT can catalyzetransesterification reactions in an aqueous medium and suggests how a serine hydrolase can be engineeredto be an efficient acyltransferase.