Properties, Purification, and Application to Determination of Asparagine in Biological Samples

After the first isolation of asparagine in 1806 by Vauquelin and Robiquet (l), there were numerous studies of its properties and physiological significance (2-4). Piria (5) in 1848 was probably the first to adduce evidence for a physiological role of asparagine during the life cycle of plants, and also to observe its transformation or metabolism by yeast. However, it was not until approximately 50 years later that clear evidence for asparaginase activity in animal tissues (6, 7) and fungi (8, 9) was obtained. Subsequent studies on a variety of animal tissues, plants, and microorganisms indicated that the occurrence of such enzymes is widespread (4, l&12). In 1922, Clementi (13) reported that among mammals, the guinea pig appeared to be unique in possessing an active asparaginase in blood serum. Partially purified enzyme preparations from this source have been utilized by several investigators (14-17) for studies on asparagine metabolism and the assay of asparagine in biological samples. From these studies, evidence regarding stability, specificity, and broad applicability of the guinea pig serum enzyme suggested that it is superior for assaying asparagine to most other asparaginases that have been described. Requirements for a relatively simple and sensitive method for the direct, quantitative determination of asparagine in blood, cerebrospinal fluid, urine, tissue-free amino acid pools, and protein enzymatic hydrolysates led us to a further study of guinea pig serum asparaginase. This paper reports investigations on the purification and properties of the enzyme and its utilization for assaying the asparagine content of a variety of biological samples. In part these studies represent a confirmation and extension of previous investigations of this enzyme reported by Meister et al. (15).