Pyrrolooxygenases: Isolation, properties, and products formed

Abstract

1. 1.|A new group of enzymes was isolated from wheat germ and rat liver which oxidized the pyrrole ring of indoles affording o-formamidophenacyl derivatives. They behaved as mixed-function oxidases and were named pyrrolooxygenases. Tryptophan, ethyl N-acetyltryptophan, skatole, 3-indoleacetic acid, 3-indolepropionic acid and indole were substrates of the pyrrolooxygenases. The enzymatic oxidations were catalyzed by at least two enzymes within the group; one acting on tryptophan and its derivatives, and the other one acting on skatole and the other indoles. 2. 2.|The pyrrolooxygenases had an absolute requirement for oxygen and an exogenous reducing agent. The reducing agents were illuminated chloroplasts for the plant enzymes, and NADPH and a microsomal transport system for the mammalian enzymes. Both could be replaced by sodium dithionite. 3. 3.|Chelating agents, such as α,α′-dipyridyl and EDTA inhibited the enzymatic activity, while sodium cyanide had no effect. The enzymes were also inactivated by dithiothreitol and mercaptoethanol. 4. 4.|A natural heat-labile macromolecular inhibitor of the pyrrolooxygenases was present in the crude extracts and was separated during the successive purification steps. 5. 5.|Formamidase (EC 3.5.1.9) activity was present in the extracts together with the pyrrolooxygenases and transformed the o-formamidophenacyl derivatives into the corresponding o-amino derivatives. During the purification steps the formylase activity was partly removed.