A novel enzyme, L-Tryptophan oxidase, from a basidiomycete, Coprinus sp SF-1: Purification and characterization

A basidiomycete, Coprinus sp. SF-1, was found to produce an L-Trp-oxidizing enzyme by screening from the culture collection of our laboratory. After s olubilization by 1 M NaSCN from the particulate fraction of disrupted cells of the strain, the enzyme was purified about 76-fold to essential homogene ity. The enzyme had a molecular mass of about 420 kDa and the subunit molec ular mass was 68 kDa. The enzyme contained 1 mol of non-covalently bound FA D per mol of the subunit. It catalyzed the simultaneous reactions of oxidat ive deamination and oxygenative decarboxylation of L-Trp to form indolepyru vic acid and indole-3-acetamide, the former of which was further oxidized t o indole-3-acetic acid. The molar ratio of the respective reaction products was about 9:1. The enzyme specifically oxidized L-Trp, and slightly acted on L-Phe and L-Tyr. The K-m for L-Trp was about 0.5 mM in both oxidase and oxygenase reactions. Thus, the enzyme is a novel one and was tentatively de signated "L-Trp oxidase (deaminating and decarboxylating)". The optimum pHs of oxidase and oxygenase activities were 7.0 and 9.0, respectively. The op timum temperatures of both activities were 50 degrees C. The enzyme was sta ble at pH 6.0-10.5 and below 50 degrees C, and at 4 degrees C for 1 year.