The Effect of cAMP on Phosphohydrolase Activity of the Barley Root Cells

We studied the effects of cAMP on phosphohydrolase activity in the microsomal fraction and its 0.5 M KCl extract. In both preparations, cAMP inhibited the activity of acid phosphatases. In the microsomal fraction, a 50% inhibition of acid cation-dependent (Mg²⁺, Cu²⁺) phosphatase was induced at pH 6.0 by 10 M cAMP; whereas, for cation-independent phosphatase, this effect was exerted only by 50 M cAMP. In the KCl extract, the sensitivity of both cation-dependent and cation-independent acid phosphatases to cAMP was higher than in the microsomal fraction. Cyclic AMP did not reduce the activity of nucleosidases. Selectivity in the cAMP action on acid phosphatases is assumed to be one of the mechanisms controlling the biochemical activity outside the barley root cells.