Properties of salicylate hydroxylase and hydroxyquinol 1,2-dioxygenase purified from Trichosporon cutaneum

Abstract

Salicylate hydroxylase (salicylate 1-monooxygenase, EC 1.14.13.1) was purified from the soil yeast Trichosporon cutaneum. The enzyme contained flavin adenine dinucleotide and was monomeric, with a molecular weight of 45,300. In addition to salicylate, the four isomeric dihydroxybenzoates having one hydroxyl adjacent to carboxyl in the benzene nucleus were oxidatively decarboxylated without formation of hydrogen peroxide. One of these isomers, gentisate, was rapidly oxidized to hydroxyquinol by the enzyme but did not serve as an effective single carbon source for T. cutaneum; however, when growing with salicylate, cells also readily utilized gentisate for growth. Hydroxyquinol 1,2-dioxygenase (EC 1.13.11....) is a newly investigated enzyme which was purified from T. cutaneum grown with 4-hydroxybenzoate. The enzyme was red, contained ferric iron, and was specific for hydroxyquinol; catechol and pyrogallol were oxidized at less than 1% of the rate for hydroxyquinol, and no activity could be detected against seven other catechols. The enzyme was composed of two nonidentical subunits having molecular weights of 39,600 and 38,200 and was apparently dimeric.