Biochemical characterization of Alr1529, a novel SGNH hydrolase variant from Anabaena sp. PCC 7120.
Alr1529, a serine hydrolase from the cyanobacteria Anabaena sp. strain PCC 7120 is a member of the SGNH hydrolase superfamily. Biochemical characterization of the purified enzyme revealed that the protein is a dimer in solution and is specific for aryl esters of short chain carboxylic acids. The enzyme was regio-selective for alpha-naphthyl esters with maximum activity at pH 7.5 and has a broad optimal temperature range (25-45 degrees C). A structure based comparison of Alr1529 with other superfamily members confirmed the presence of the catalytic triad (Ser17-Asp179-His182) and oxyanion hole (Ser17-Arg54-Asn87) residues. Alr1529 exhibits a previously undescribed variation in the active site wherein a conserved Gly, a proton donor making up the oxyanion hole in the SGNH hydrolases, is substituted by Arg54. Site-directed mutagenesis studies suggest that Arg54 is crucial for substrate binding and catalytic activity. Ser17 plays a very crucial role in catalysis as evident from the 50-fold lower activity of the S17A mutant.
Bakshy
Kiranmayee
K
Department of Biotechnology, Indian Institute of Technology Madras, Chennai 600 036, India.
Gummadi
Sathyanarayana N
SN
Manoj
Narayanan
N
D000595:Amino Acid Sequence; D017033:Anabaena / Q000201:enzymology*; D002118:Calcium / Q000737:chemistry; D002384:Catalysis; D020134:Catalytic Domain; D002413:Cations, Divalent; D003300:Copper / Q000737:chemistry; D004950:Esterases / Q000737:chemistry* / Q000235:genetics; D005296:Ferrous Compounds / Q000737:chemistry; D006868:Hydrolysis; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D055503:Protein Multimerization; D012694:Serine / Q000235:genetics; D013379:Substrate Specificity
D002413:Cations, Divalent; D005296:Ferrous Compounds; D012694:Serine; D003300:Copper; D004950:Esterases; D002118:Calcium