Crystal structure of Saccharomyces cerevisiae Aro8, a putative α-aminoadipate aminotransferase

Abstract

α-Aminoadipate aminotransferase (AAA-AT) catalyzes the amination of 2-oxoadipate to a-aminoadipate in the fourth step of the a-aminoadipate pathway of lysine biosynthesis in fungi. The aromatic aminotransferase Aro8 has recently been identified as an AAA-AT in Saccharomyces cerevisiae. This enzyme displays broad substrate selectivity, utilizing several amino acids and 2-oxo acids as substrates. Here we report the 1.91A ° resolution crystal structure of Aro8 and compare it to AAAAT LysN from Thermus thermophilus and human kynurenine aminotransferase II. Inspection of the active site of Aro8 reveals asymmetric cofactor binding with lysine-pyridoxal-5-phosphate bound within the active site of one subunit in the Aro8 homodimer and pyridoxamine phosphate and a HEPES molecule bound to the other subunit. The HEPES buffer molecule binds within the substratebinding site of Aro8, yielding insights into the mechanism by which it recognizes multiple substrates and how this recognition differs from other AAA-AT/kynurenine aminotransferases. © 2013 The Protein Society.