Benzylamine oxidase and histaminase: purification and crystallization of an enzyme from pig plasma

Abstract

The enzyme benzylamine oxidase of pig plasma has been purified and some of the properties of the pure preparation have been studied. The purification procedure included several precipitations with ammonium sulphate and separations of proteins by column chromatography, first on DEAE-cellulose, followed by DEAE-Sephadex and lastly on a hydroxyapatite column. Crystals were prepared from solutions of the purified enzyme by adding ammonium sulphate. The crystalline preparation was homogeneous when studied by starch-gel electrophoresis and by ultracentrifugation. The molecular weight, as determined on the analytical ultracentrifuge, was 195 000. The copper content of the enzyme, as determined by radioactivation analysis, was about four atoms of Cu per molecule of enzyme. Concentrated solutions of the enzyme had a pink colour; the colour disappeared when substrate (benzylamine) was added under anaerobic conditions. The amines which were tested and found to be oxidized by the pure enzyme were: benzylamine, histamine, mescaline and 4-picolylamine. The affinity of the enzyme for benzylamine was more than one hundred times that for histamine.