A new assay for l-asparagine synthetase

Abstract

A fast, relatively inexpensive method of measuring the enzymatic formation of l-asparagine from l-aspartate is presented. This radiochemical assay requires simple manipulations making it ideal for working with large numbers of samples, while maintaining high sensitivity and reproducibility. A mechanism similar to the enzymatic β-decarboxylation of aspartate is utilized but in a nonenzymatic reaction. In the presence of pyridoxal and Al 3+ ions, the 14C of l-[4- 14C]aspartate is decarboxylatd while l-[4- 14C]asparagine remains intact. This assay is shown to be suitable for measuring mammalian l-asparagine synthetase activity, while not requiring the isolation of assay enzymes.