Characterization of the Bifunctional Aminoglycoside-Modifying Enzyme ANT(3' ')-Ii/AAC(6')-IId from Serratia marcescens

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• 作者：Choonkeun Kim ; Dusan Hesek ; Jaroslav Zají ; //pubs.acs.org/images/entities/ccaron.gif" border="0">ek ; Sergei B. Vakulenko ; and Shahriar Mobashery
• 刊名：Biochemistry
• 出版年：2006
• 出版时间：July 11, 2006
• 年：2006
• 卷：45
• 期：27
• 页码：8368 - 8377
• 全文大小：126K
• 年卷期：v.45,no.27(July 11, 2006)
• ISSN：1520-4995

文摘

A newly discovered bifunctional antibiotic resistance enzyme from Serratia marcescenscatalyzes adenylation and acetylation of aminoglycoside antibiotics. The structure assignment of the enzymicproducts indicated that acetylation takes place on the 6'-amine of kanamycin A and the adenylation on3' '- and 9-hydroxyl groups of streptomycin and spectinomycin, respectively. The adenyltransferase domainappears to be highly specific to spectinomycin and streptomycin, while the acetyltransferase domain showsa broad substrate profile. Initial velocity patterns indicate that both domains follow a sequential kineticmechanism. The use of dead-end and product inhibition, the solvent isotope effect, and the solvent viscosityeffect reveals that the adenyltransferase domain catalyzes the reaction by a Theorell-Chance kineticmechanism, where ATP binds to the enzyme prior to the aminoglycoside and the modified antibiotic isthe last product to be released. The acetyltransferase domain follows an ordered bi-bi kinetic mechanism,in which the antibiotic is the first substrate that binds to the active site and CoASH is released prior tothe modified aminoglycoside. The merging of two genes to create bifunctional resistance enzymes withexpanded profiles has now been documented in four instances, including the subject of study in thisreport, which suggests a new trend in the emergence of resistance to aminoglycoside antibiotics amongpathogens.