AbstractsChemistry

Partial purification of diamine oxidase from pea seedlings, Pisum sativum, was accomplished by homogenization of 8-10 day etiolated epicotyl tissue, followed by ammonium sulfate fractionation and DEAE Sephadex column chromatography. The preparation thus obtained was purified 50 fold. Some properties of this enzyme were investigated. A radio-tracer method was adapted for assay of diamine oxidase with tryptamine. The oxidation product of tryptamine was characterized by sodium borohydride reduction and subsequent repeated crystallizations of the reduced species with unlabeled tryptophol. The Michaelis constants for tryptamine and putrescine were determined with purified diamine oxidase; the values obtained at pH 8 were 4 x 10⁻⁴M for tryptamine and 7.4 x 10⁻⁵ M for putrescine. The titration of diamine oxidase was accomplished with several hydrazines. Beta-hydroxyethylhydrazine (BOH) gave a more pronounced inhibitory effect than 1, 1-dimethylhydrazine (UDMH) or hydrazine. The rates of inhibition of diamine oxidase with these inhibitors were examined and the initial rapid interaction of hydrazines with the enzyme was found to be second-order and dependent upon inhibitor concentration. The inhibition of diamine oxidase activity by these hydrazines was not reversed by dialysis.