Tryptophan synthetase in shoot and root tissue of pea seedlings

Abstract

The occurrence of tryptophan synthetase in excised tomato root cultures (Lycopersicon esculentum Mill. var. Red River) and pea seedlings (Pisum sativum L. var. Alaska) was examined using cell-free extracts. No tryptophan synthetase activity could be detected in the former. Using serine-14C and indole-14C, with extracts from peas, it is shown by chromatographic and radioautographic methods that tryptophan is the product of the reaction, that both the substrates are necessary, and that pyridoxal phosphate is a necessary cofactor. Inhibition by metal ions, lability, thermolability, and various other properties are described. Partial purification was effected by gel filtration. The enzyme activity in pea root extracts, as measured by indole utilization per unit fresh weight, is much lower than in the enzyme preparations from terminal buds. A system causing destruction of indole, other than tryptophan synthetase, is also present in crude root extracts.