A New Potent Kinin-inactivating Enzyme from the Mushroom Psalliota hortensis

Abstract

A new potent kinin-inactivating enzyme was purified from a kind of Japanese mushroom, Psalliota hortensis (Tsukuritake, in Japanese), by means of water extraction, ammonium sulfate fractionation, DEAE-Sephadex A-50 chromatography and Sephadex G-100 gel filtration. The final enzyme preparation had an activity of 2284 kininase U/E₂₈₀, which is the highest known among kininases derived from plants. This enzyme cleaved Gly⁴-Phe⁵ and Phe⁵-Ser⁶ bonds of the bradykinin molecule. Its molecular weight was estimated to be 6.7×10⁴ and the optimum pH for the degradation of bradykinin was 8.0. The enzymatic activity of this enzyme was inhibited by mercurials, diisopropyl-fluorophosphate (DFP) and a high concentration of ethylenediaminetetraacetic acid (EDTA), but tosyllysine chloromethyl ketone (TLCK), tosylphenylalanine chloromethyl ketone (TPCK), iodoacetic acid, Trasylol and sodium tetrathionate had no detectable effect.