Diamine oxidase: molecular weight and subunit analysis.

Electrophoretically pure hog kidney diamine oxidase has been isolated by an improved procedure and subjected to molecular weight and subunit analyses. Sedimentation/diffusion and sedimentation equilibrium ultracentrifugation clearly show that the native enzyme has a molecular weight of 172,000. Acrylamide gel electrophoresis indicates that the enzyme consists of two apparently identical subunits of 91,000 daltons each. The native enzyme contains two firmly bound Cu(II) ions. The isolation procedure described provides diamine oxidase in 50–60% yield of activity and of the highest specific activity yet reported (1.2 units/mg).