A NEW OLD YELLOW ENZYME OF SACCHAROMYCES-CEREVISIAE

In 1993, the first gene of Old Yellow Enzyme (OYE) of Saccharomyces ce revisiae was cloned (Stott, K,, Saito, K,, Thiele, D. J,, and Massey, V, (1993) J, Biol, Chem, 268, 6097-6106) and named OYE2 to distinguish it from the first OYE gene cloned from Saccharomyces carlsbergenesis (Saito, K,, Thiele, D, J,, Davio, M,, Lockridge, O., and Massey, V, (1 991) J, Biol, Chem, 266, 20720-20724), The analysis of an OYE2 deletio n mutant suggested that S, cerevisiae had at least two OYE genes. In t he present study, we cloned a new OYE species named OYE3 and analyzed the OYE3 protein expressed in Escherichia coli, OYE3 consists of 400 a mino acid residues and its molecular mass calculated by electrospray m ass spectrometry is 44,788 daltons, in good agreement with the value o f 44,920 daltons predicted from the amino acid sequence derived from t he DNA sequence, In the downstream region of the OYE3 gene, the cytoch rome oxidase (COX10) gene exists with a 426-base pair intermediate seq uence, Some of the physicochemical and kinetic properties of OYE2 and OYE3 have been determined. Although the two enzymes are clearly closel y related, they show differences in ligand binding properties and in t heir catalytic activities with oxygen and cyclohexen-2-one as accepter s.