8] Enzymatic determination of glutamine and asparagine

Abstract

This chapter describes the procedure used in enzymatic determination of glutamine and asparagines. The procedures are designed to determine L-asparagine and L-glutamine in minimal amounts of samples by highly specific enzymatic methods. The applicability of the procedures to analyses of biological fluids, tissues, and hydrolyzates of proteins or peptides are demonstrated and are verified by independent methods. The procedures are designed for the conditions and ranges specified. L-asparagine can be measured by determination of ammonia or L-aspartate. The assay procedure is based on determination of the ammonia liberated. Asparaginase preparations from yeast, Escherichia coli , and liver are also described and sources from plants and animal tissues are reviewed. L-glutamine is measured by determination of ammonia, carbon dioxide, and γ-aminobutyric acid. The assay procedure is based on determination of the ammonia liberated. The L-glutaminase clearly differs from glutaminases isolated from animal tissues in terms of pH optimum, anion activation, effects of α-keto acids, and specificity. The determination of ammonia by the Conway-Russell procedure is also discussed.