A radiometric technique for measuring l-asparagine in picomol quantities

Abstract

A radiometric technique for measuring l-asparagine in small samples of biological origin is presented. After removal of l-glutamate and l-aspartate by enzymic decarboxylation, l-asparagine in the sample is hydrolysed to l-aspartate with l-asparaginase from Escherichia coli. The l-aspartate so generated is then enzymically transaminated with 2-oxo[1-14C]glutarate yielding l-[1-14C]glutamate. After specific chemical removal of unchanged 2-oxo[1-14C]glutarate, the l-[1-14C]glutamate generated is determined by scintillation counting of the radioactivity. This technique can measure the concentration of l-asparagine present in approx. 1μl of mouse blood, and is capable of detecting as little as 25pmol of the amide. Illustrative applications of the method are presented and discussed, including measurement of the l-asparagine content of the mouse hypophysis.