A new method for the determination of ligand dissociation rate constant of carboxyhemoglobin.

Concanavalin A (Con A) treatment of plasma membrane-enriched fractions from lactating mammary gland causes an activation of Mg⁺⁺-ATPase and an inactivation of 5′-nucleotidase. Both effects can be prevented by the presence of α-methylmannoside, and both exhibit cooperativity with Hill coefficients near 2. The cooperativity may arise from Con A effects on subunit interactions of the enzymes or by clustering of the enzyme molecules in the membrane, possibly induced by Con A. Investigations of these systems should be useful for developing an understanding of modes of action of Con A in complex phenomena.