l-Lysine Decarboxylase: Preparation of Specific Enzyme and Coenzyme

Abstract

STRAINS of certain bacteria produce specific amino-acid decarboxylases when grown under acid conditions¹. A cell-free preparation of l(+)-lysine decarboxylase has been made from acetone-dried powders of selected strains of coliform organisms grown for 24 hr. at 25° in 2 per cent glucose caseindigest-broth. A suitable paracolon organism, Bact. cadaveris, has been deposited in the National Collection of Type Cultures*. The powder is extracted for 2 hr. at 37° with X ml. M/45 borate buffer pH 8.5 (1 ml. per 20 mgm. powder) and the sediment then centrifuged off. Ethanol is added to the supernatant to a concentration of 20 per cent, the pH. adjusted to 5 with acetic acid and X/2 ml. alumina C? suspension (16 mgm./ml.) added immediately. The alumina is twice eluted with X/2 ml. M/5 phosphate pH. 7.0 and the enzyme precipitated from the combined eluates by the addition of 50 gm. solid ammonium sulphate per 100 ml. The precipitate is dissolved in water and insoluble material centrifuged off. The opalescent supernatant fluid can be used as a source of specific enzyme or purified a further 10–12 times by fractional ammonium sulphate precipitation as shown in the accompanying table.