title: Gene identification and structural characterization of the pyridoxal 5'-phosphate degradative protein 3-hydroxy-2-methylpyridine-4,5-dicarboxylate decarboxylase from mesorhizobium loti MAFF303099.
abstract: 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 enzyme involved in the catabolism of pyridoxal 5'-phosphate (Vitamin B6). This enzyme was overexpressed in Escherichia coli and characterized. HMPDdc is a 26 kDa protein that catalyzes the decarboxylation of 3-hydroxy-2-methylpyridine-4,5-dicarboxylate to 3-hydroxy-2-methylpyridine-5-carboxylate. The KM and kcat were found to be 366 microM and 0.6 s-1, respectively. The structure of this enzyme was determined at 1.9 A resolution using SAD phasing and belongs to the class II aldolase/adducin superfamily. While the decarboxylation of hydroxy-substituted benzene rings is a common motif in biosynthesis, the mechanism of this reaction is still poorly characterized. The structural studies described here suggest that catalysis of such decarboxylations proceeds by an aldolase-like mechanism.
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Tathagata
authors.initials: T
authors.lastname: Mukherjee
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: McCulloch
authors.forename: Steven E
authors.initials: SE
authors.lastname: Ealick
authors.forename: Tadhg P
authors.initials: TP
authors.lastname: Begley
mesh_terms: D020561:Alphaproteobacteria / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics* / Q000302:isolation & purification; D001665:Binding Sites; D002262:Carboxy-Lyases / Q000737:chemistry* / Q000235:genetics* / Q000302:isolation & purification; D002384:Catalysis; D003001:Cloning, Molecular; D007700:Kinetics; D008958:Models, Molecular; D011732:Pyridoxal Phosphate / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D011732:Pyridoxal Phosphate; D002262:Carboxy-Lyases