The glycoprotein nature of pig kidney diamine oxidase. Role of disulphide groups and arginine residues in the concanavalin A-diamine oxidase interaction.

Pig kidney diamine oxidase (DAO) was found to contain 5% (w/w) natural hexose, 3.25% glucosamine, 2.61% N-acetylglucosamine and 0.25% N-acetylneuraminic acid. The enzyme exhibited strong affinity towards concanavalin A (Con A) with a stoichiometry of 1:4.6. The kinetics of interaction approached an apparent first-order rate, with a rate constant (Kapp.) value of 1.5 x 10(-2) min-1. The enzyme reduced with dithiothreitol followed by alkylation with iodoacetamide showed an increase in the stoichiometry of the Con A-DAO interaction. Similarly arginine modification by phenylglyoxal caused decreased affinity, with an altered Kapp. value of 9.09 x 10(-3) min-1. The results suggest that, besides the carbohydrate content, the protein moiety of the enzyme also plays a significant role in the Con A-DAO interaction.