A facile enzymatic method for the location of radioactivity associated with the carbons of L-aspartic acid, L-asparagine, and beta-cyano-L-alanine.

A radiometric enzymatic technique has been devised for locating radioactivity in the carbon skeleton of l-aspartic acid, l-asparagine, and β-cyano-l-alanine. l-Asparaginase at demonstrably discriminant concentrations is used to hydrolyze l-asparagine and/or β-cyano-l-alanine to l-aspartic acid, which in turn is transaminated to oxaloacetic acid by l-glutamate oxaloacetate transaminase. The β-carboxyl group of oxaloacetate is detached by zinc ions, and the radiolabeled CO₂ is collected in alkali after diffusion. The residual pyruvic acid is α-decarboxylated by pyruvate decarboxylase to CO₂, which is collected in a second alkaline trap, and the other product of decarboxylation, acetaldehyde, diffuses into a separate semicarbazide trap. Carbons 4, 1, and 3 plus 2 are located in this order. This method is shown to be facile, sensitive, reliable, and applicable to samples of biological origin.