Purification of pig-kidney diamine oxidase and its identity with histaminase

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Abstract
Pig-kidney diamine oxidase was purified by controlled heat denaturation, pH precipitation, ammonium sulphate fractionation, column electrophoresis and column chromatography on DEAE-cellulose. The procedure gave 1700-fold purification. The copper content of the enzyme preparations increased during purification to about 0.06%. It is suggested that pig-kidney diamine oxidase is a copper-containing protein. The purified enzymes was strongly activated by the addition of pyridoxal phosphate. The effects of pH and substrate concentration on diamine-oxidase and histaminase activities were investigated with both a crude preparation and the purified enzyme. A pig-kidney-cortex extract containing diamine-oxidase and histaminase activities was fractionated by column chromatography on DEAE-cellulose and CM-cellulose and by column electrophoresis. The ratio of cadaverine-oxidase activity to histaminase activity remained about constant at all stages of purification. It is concluded that pig-kidney diamine-oxidase and histaminase activities are present in the same enzyme.