STUDIES WITH'THE FLAVIN DEPENDENT ALCOHOL OXIDASE FROM YEAST: PROPERTIES AND CATALYTIC MECHANISM

vntroduct ion Alcohol oxidase (E.C. 1, 1.3. 13) from candida boidinii (octaner, M r subunit 74000, 1 FAD/subunit) catalyzes the oxidation of primary alcohols: RCH20H + O2- RCHO + H202 • The native enzyrre stabilizes a FAD radical,e Fl. =, even in the presence of oxygen and substrate (1,2). The arcount of Fl ' (approx. 30 % of FAD of our enzyne) is increased 2.5 fold by hydroxyl-amine with concomitant quantitative inactivation of the enzyne (1). Fl' is considered to be catalvtically inactive. Otherwise Ettle is known on the catalytic rrechanism: Cyclopropanol (2) and cvclopropanone (3,4) irre-versiblv inactivate the enzyne probably via radical pathways. In contrast to several other flavin oxidases (5) a-alkvnoic substrates are not suicide inhibitors of alcohol oxidase: Upon turnover of propargyl alcohol inacti-vation is observed but is claimed to be due to reaction of the accumula-ting propynal with an active side residue (6). v' Results and Discussion 'Ihe catalytic activitv of alcohol oxidase is increased 1.7 fold in the pre-sence of the redox dve radical ABI'S ' + (Hq. 1) which is produced via the.peroxidase(PCD) catalvzed oxidation of 2,2 '-azino-bis- 13-ethylbenzthiazo-line-sulfonic acid-6) (ABI'Sred) by HP2 (7). ABI'S'+ might react with Fl'-to give ABTSred and Fl ox ' The electron soectrum of the activated enzyne also indicates the loss of. Fl '- upon ABTS ' +-treatment (Hg. 1). This sup