Plasmodium falciparum Sir2 is an NAD+-Dependent Deacetylase and an Acetyllysine-Dependent and Acetyllysine-Independent NAD+ Glycohydrolase

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• 作者：Jarrod B. French ; Yana Cen ; Anthony A. Sauve
• 刊名：Biochemistry
• 出版年：2008
• 出版时间：September 23, 2008
• 年：2008
• 卷：47
• 期：38
• 页码：10227-10239
• 全文大小：345K
• 年卷期：v.47,no.38(September 23, 2008)
• ISSN：1520-4995

文摘

Sirtuins are NAD⁺-dependent enzymes that deacetylate a variety of cellular proteins and in some cases catalyze protein ADP-ribosyl transfer. The catalytic mechanism of deacetylation is proposed to involve an ADPR-peptidylimidate, whereas the mechanism of ADP-ribosyl transfer to proteins is undetermined. Herein we characterize a Plasmodium falciparum sirtuin that catalyzes deacetylation of histone peptide sequences. Interestingly, the enzyme can also hydrolyze NAD⁺. Two mechanisms of hydrolysis were identified and characterized. One is independent of acetyllysine substrate and produces α-stereochemistry as established by reaction of methanol which forms α-1-O-methyl-ADPR. This reaction is insensitive to nicotinamide inhibition. The second solvolytic mechanism is dependent on acetylated peptide and is proposed to involve the imidate to generate β-stereochemistry. Stereochemistry was established by isolation of β-1-O-methyl-ADPR when methanol was added as a cosolvent. This solvolytic reaction was inhibited by nicotinamide, suggesting that nicotinamide and solvent compete for the imidate. These findings establish new reactions of wildtype sirtuins and suggest possible mechanisms for ADP-ribosylation to proteins. These findings also illustrate the potential utility of nicotinamide as a probe for mechanisms of sirtuin-catalyzed ADP-ribosyl transfer.