Studies on the carbohydrate moiety of dopamine beta-hydroxylase: interaction of the enzyme with concanavalin A

Abstract

Dopamine beta-hydroxylase [EC 1.14.17.1; 3,4-dihydroxyphenylethylamine, ascorbate:oxygen oxidoreductase (beta-hydroxylating)], a glycoprotein, was found to interact strongly with the plant lectin, concanavalin A. This interaction did not appear to alter the catalytic properties of the enzyme and did not prevent interaction of the protein with specific antibodies. Dopamine-beta-hydroxylase is adsorbed to concanavalin A covalently bound to Sepharose and can be eluted with alpha-methylmannoside. The enzyme is catalytically active when it is immobilized on a concanavalin A-Sepharose column. Enzymic removal of four of seven mannose residues present in the monomer does not result in the loss of any catalytic activity. It is concluded that the active site is not near the point of carbohydrate attachment on the molecule and that this may be of significance in orienting the enzyme on the vesicular membrane.