BOVINE ADRENAL MEDULLARY DOPAMINE-β-HYDROXYLASE: STUDIES ON INTERACTION WITH CONCANAVALIN A

Bovine adrenal medullary dopamine-β-hydroxylase binds with concanavalin A and forms an enzymically active precipitate. The formation of the insoluble complex is pH-dependent and can be inhibited by α-methyl-D-mannoside, D-mannose and D-glucose. The insoluble complex can be dissociated into two species with α-methyl-D-mannoside. From the results, it appears that the interaction between dopamine-β-hydroxylase and concanavalin A is due to the carbohydrate moiety of dopamine-β-hydroxylase. This property was used to purify the enzyme from a soluble lysate of chromaffin granules. Of all the proteins contained in the soluble lysate, dopamine-β-hydroxylase was the only one to be retained on a column of concanavalin A covalently bound to Sepharose 4B. The preparation of pure dopamine-β-hydroxylase exhibits a very high specific activity of 320 μmol of octopamine formed per 30 min per mg of protein.