Abstract
An improved method of radiochemical assay of An Improved Method of Radiochemical Assay of δ-Aminolevulinate Synthetase and Its Application to the Study of the Level of Hepatic δ-Aminolevulinate Synthetase in Normal Rat-aminolevulinate (ALA) synthetase was described which enabled us to study the behaviour of ALA synthetase in the liver cytosol of normal rat. When hemin was administered to the normal rat, the level of ALA synthetase in the liver mitochondria decreased markedly and the level in the liver cytosol also decreased slightly. Therefore the total activity of ALA synthetase in the liver of normal rat declined sharply after the hemin administration. Under the physiological conditions in the normal rat, the regulatory role of hemin in the control of por-phyrin synthesis may be ascribed mainly to the inhibition of synthesis of ALA synthetase rather than the inhibition of transfer of ALA synthetase from the liver cytosol into mitochondria.
