Effect of concanavalin A on tyrosine aminotransferase in rat hepatoma tissue culture cells. Rapid reversible inactivation of soluble enzyme.
Concanavalin A added to intact cells at 37 degrees caused rapid and reversible inactivation of a soluble enzyme, tyrosine aminotransferase, in two lines of rat hepatoma tissue culture cells grown in monolayer culture. This temperature-dependent process was independent of de novo protein and RNA synthesis and independent of increased uptake of Ca2+ and Mg2+ or glucose. The inactivation could be reversed by adding alpha-methyl-D-mannopyranoside a competing sugar for concanavalin A binding. Other lectins known to bind to different sugars did not bring about the inactivation of tyrosine aminotransferase. Addition of concanavalin A did not result in the inactivation of another soluble enzyme, lactic dehydrogenase. The maintenance of tyrosine aminotransferase in an inactive form after the binding of concanavalin A to the cells required the continued presence of concanavalin A. This effect of concanavalin A could not be mimicked either by dibutyryl cyclic adenosine or guanosine monophosphoric acid. Incubation of cell extracts with concanavalin A did not result in inactivation nor did mixing of extracts from concanavalin A-treated cells with extracts from untreated cells. On the basis of these results we conclude that the following are the essential requirements for concanavalin A to bring about the inactivation of tyrosine aminotransferase: (a) the binding of native concanavalin A to the cells; (b) integrity of certain structural elements of the cells.
Effect of concanavalin A on tyrosine aminotransferase in rat hepatoma tissue culture cells. Rapid reversible inactivation of soluble enzyme. Concanavalin A added to intact cells at 37 degrees caused rapid and reversible inactivation of a soluble enzyme, tyrosine aminotransferase, in two lines of rat hepatoma tissue culture cells grown in monolayer culture. This temperature-dependent process was independent of de novo protein and RNA synthesis and independent of increased uptake of Ca2+ and Mg2+ or glucose. The inactivation could be reversed by adding alpha-methyl-D-mannopyranoside a competing sugar for concanavalin A binding. Other lectins known to bind to different sugars did not bring about the inactivation of tyrosine aminotransferase. Addition of concanavalin A did not result in the inactivation of another soluble enzyme, lactic dehydrogenase. The maintenance of tyrosine aminotransferase in an inactive form after the binding of concanavalin A to the cells required the continued presence of concanavalin A. This effect of concanavalin A could not be mimicked either by dibutyryl cyclic adenosine or guanosine monophosphoric acid. Incubation of cell extracts with concanavalin A did not result in inactivation nor did mixing of extracts from concanavalin A-treated cells with extracts from untreated cells. On the basis of these results we conclude that the following are the essential requirements for concanavalin A to bring about the inactivation of tyrosine aminotransferase: (a) the binding of native concanavalin A to the cells; (b) integrity of certain structural elements of the cells.