The Effects of Urea and Salts of Ammonium Phosphate on Salivary Amylase

Abstract

Urea in concns. up to 1.45 [image] (8.7%) is without inhibitory effect on salivary amylase in vitro except under conditions which lead to progressive, apparently irreversible inactivation of the amylase. Urea promotes this inactivation and thereby causes a marked inhibition of amylase activity. Such inhibition occurs during prolonged contact between enzyme and urea at 37[degree]C in the absence of alkali metal or ammonium salts and during short periods of contact between urea and amylase at temps. above the optimum for amylase activity even in the presence of antidenaturant salts. Urea appears to have no effect on reversibly-denatured amylase as judged by the absence of inhibition at 39[degree]C when salts are present and the inability of high hydrostatic pressure to reverse the inhibition by urea at 50[degree]C. Apparently urea would be without effect on amylase in vivo in concns. resulting from the use of ammoniated dentifrices even under conditions of frequent or prolonged use.