The effect of gradual mild acid hydrolysis on serologic activities of glycoproteins from human erythrocytes.

M and N blood group glycoproteins from O group erythrocytes were hydrolyzed with acid under various conditions that produced a gradual release of sialic acid. The preparations desialized to different degree were tested for M, N, NVg and AHp activities. M and N blood group activity was decreased upon release of sialic acid, and AHp activity was exposed "de novo" and increased upon desialization. NVg activity always increased during the initial period of acid hydrolysis, but prolonged heating in acid solution caused subsequent partial inactivation of glycoprotein. This decrease in NHp activity was not related either to the extent of desialization, or to fragmentation of the glycoprotein molecule.