Gene Identification and Structural Characterization of the Pyridoxal 5'-Phosphate Degradative Protein 3-Hydroxy-2-methylpyridine-4,5-dicarboxylate Decarboxylase from Mesorhizobium loti MAFF3030

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• 作者：Tathagata Mukherjee ; Kathryn M. McCulloch ; Steven E. Ealick ; Tadhg P. Begley
• 刊名：Biochemistry
• 出版年：2007
• 出版时间：November 27, 2007
• 年：2007
• 卷：46
• 期：47
• 页码：13606 - 13615
• 全文大小：624K
• 年卷期：v.46,no.47(November 27, 2007)
• ISSN：1520-4995

文摘

The function of the mlr6791 gene from Mesorhizobium loti MAFF303099 has been identified.This gene encodes 3-hydroxy-2-methylpyridine-4,5-dicarboxylate decarboxylase (HMPDdc), an enzymeinvolved in the catabolism of pyridoxal 5'-phosphate (Vitamin B₆). This enzyme was overexpressed inEscherichia coli and characterized. HMPDdc is a 26 kDa protein that catalyzes the decarboxylation of3-hydroxy-2-methylpyridine-4,5-dicarboxylate to 3-hydroxy-2-methylpyridine-5-carboxylate. The K_M andk_cat were found to be 366 M and 0.6 s^-1, respectively. The structure of this enzyme was determined at1.9 Å resolution using SAD phasing and belongs to the class II aldolase/adducin superfamily. While thedecarboxylation of hydroxy-substituted benzene rings is a common motif in biosynthesis, the mechanismof this reaction is still poorly characterized. The structural studies described here suggest that catalysis ofsuch decarboxylations proceeds by an aldolase-like mechanism.