[Enzymatic activity of glycoprotein catabolism in the organs of rats with hyper- and hypovitaminosis A].

Activities of glycosidases neuromanidase, alpha-L-fucosidase, beta-galactosidase and beta-N-acetylglucosaminidase were studied in rat small intestine and liver tissue under conditions of hyper- and hypovitaminosis A. Both excessive and insufficient administrations of vitamin A were accompanied by distinct alterations in activity of the enzymes studied in small intestine and (although less distinct) in liver tissue. The most significant dependence on the presence of vitamin A exhibited beta-galactosidase and especially alpha-L-fucosidase, activity of which was decreased in hypervitaminosis and increased in hypovitaminosis A. Activity of neuraminidase was usually slightly altered but its marked activation was noted in liver tissue under conditions of hypervitaminosis A. Vitamin A appears to participate in allosteric control of the glycosidase activity in small intestine and in catabolism of glycoproteins. The alterations of the enzymatic activity found in hyper- and hypovitaminosis A might be responsible for changes in composition of membrane glycoproteins and, hence, for the typical for vitamin A disbalance impairments in cellular growth and differentiation.