TAILIEUCHUNG - Báo cáo khoa học: Characterization of a thiamin diphosphate-dependent phenylpyruvate decarboxylase from Saccharomyces cerevisiae

The product of theARO10gene from Saccharomyces cerevisiaewas ini-tially identified as a thiamine diphosphate-dependent phenylpyruvate decar-boxylase with a broad substrate specificity. It was suggested that the enzyme could be responsible for the catabolism of aromatic and branched-chain amino acids, as well as methionine. | IFEBS Journal Characterization of a thiamin diphosphate-dependent phenylpyruvate decarboxylase from Saccharomyces cerevisiae Malea M. Kneen1 Razvan Stan1 Alejandra Yep2 Ryan P. Tyler2 Choedchai Saehuan2 and Michael J. McLeish1 1 Department of Chemistry and ChemicalBiology Indiana University-Purdue University Indianapolis IN USA 2 Department of MedicinalChemistry University of Michigan Ann Arbor MI USA Keywords amino acid catabolism Ehrlich pathway homology model mutagenesis TPP Correspondence M. J. McLeish Department of Chemistry and ChemicalBiology Indiana University-Purdue University Indianapolis 402 North Blackford Street Indianapolis IN 46202 USA Fax 1 317 274 4701 Tel 1 317 274 6889 E-mail mcleish@ Present address Department of MedicalTechnology Faculty of Allied Health Sciences Naresuan University Phitsanulok Thailand Received 23 December 2010 revised 7 March 2011 accepted 21 March 2011 doi The product of the ARO10 gene from Saccharomyces cerevisiae was initially identified as a thiamine diphosphate-dependent phenylpyruvate decarboxylase with a broad substrate specificity. It was suggested that the enzyme could be responsible for the catabolism of aromatic and branched-chain amino acids as well as methionine. In the present study we report the overexpression of the ARO10 gene product in Escherichia coli and the first detailed in vitro characterization of this enzyme. The enzyme is shown to be an efficient aromatic 2-keto acid decarboxylase consistent with it playing a major in vivo role in phenylalanine tryptophan and possibly also tyrosine catabolism. However its substrate spectrum suggests that it is unlikely to play any significant role in the catabolism of the branched-chain amino acids or of methionine. A homology model was used to identify residues likely to be involved in substrate specificity. Site-directed mutagenesis on those residues confirmed previous studies indicating that mutation of single residues is

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