The Effects of Phosphate on the Development of Phytase in the Wheat Embryo

The effects of experimentally induced changes of inorganic phosphate concentration in the tissues of isolated wheat embryos during germination, were investigated in order to study the control mechanisms of the phytin-phytase system. The supply of inorganic phosphate at concentrations from 5 × 10^?3M to 3 × 10^?3M does not alter growth, respiration, hexose phosphate level and protein synthesis, measured both as ¹⁴C leucine incorporation and as increase of several enzymatic activities. Experiments with ³²P inorganic phosphate indicate that the rate of phvtin breakdown is controlled in vivo by the concentration of inorganic phosphate, through the inhibition of phytase activity. Phytase increases during germination: this increase, sensitive to puromycin, is specifically repressed by inorganic phosphate. An interpretation of the behaviour of the phytin-phytase system during germination under physiological conditions is tentatively given on the basis of the results obtained.