An enzymatic technique is presented for measuring N-phosphonacetyl-L-aspartic acid (PALA;NSC-224131) in biologic specimens. Tightly bound PALA is quantitatively detached from its target enzyme, L-aspartic acid transcarbamylase (ATCase), by heating at 95°C for 5 minutes. Denatured proteins are removed by centrifugation. PALA in the supernatant fluid is quantitated by exposing intact splenic ATCase to representative aliquots or subdilutions of the resultant supernatant in the presence of L-(4- 14C) aspartic acid and carbamyl phosphate. After 30 minutes' incubation at 37°C, unreacted L-[4- 14C] ) aspartic acid is dissipated enzymatically and newly formed (4- 14C)carbamyl-L-aspartic acid is quantitated by scintillation spectrometry. The percentage inhibition of ATCase responds in a linear way to the logarithm of the concentrations of PALA between 0.10 and 1.00 μM. The PALA concentration of an unknown is determined indirectly by matching the percentage inhibition caused by the unknown to the inhibition caused by a known series of standard concentrations of PALA over the linear range. This assay is sensitive, adequately reproducible despite the use of an unpurified enzyme, and easy. It can be used to measure PAHA in plasma, urine, tissues, and tumors of subjects treated with this new oncolytic drug.
|Original language||English (US)|
|Number of pages||5|
|Journal||Cancer Treatment Reports|
|State||Published - Dec 1 1978|
ASJC Scopus subject areas
- Cancer Research