Indole-3-Ethanol Oxidase in Phycomyces blakesleeanus Bgff: Characterization of the Enzyme

Indole-3-ethanol oxidase (IEt oxidase) from Phycomyces blakesleeanus Bgff.(P.b.) is a 56 kD polypeptide as determined by gel filtration. The reaction products are indole-3-acetaldehyde (IAAld) and, possibly, H(2)O(2). Enzyme activity (33-45% ammonium sulfate fraction) shows a broad pH optimum and simple Michaelis-Menten kinetics (K(m) 7 micromolar, Hill coefficient 0.95). Flavin adenine dinucleotide increases enzyme activity particularly under anaerobic conditions. Iodoacetate and HgCl(2) drastically inhibit the enzyme. With IAAld, product inhibition is observed at micromolar concentrations. IAA and some other acidic substituted indoles reduce enzyme activity but only at higher concentrations.