F. Lipmann

Abstract: Publisher Summary Carbamyl phosphate can be formed through the reaction of KH 2 P0 4 with KCNO. When the reaction is complete, potassium and most of the inorganic phosphate are removed simultaneously as the perchlorate and as the lithium salt, respectively, by the addition of lithium perchlorate. Lithium carbamyl phosphate is obtained from the filtrate by alcohol fractionation. carbamyl phosphate conveniently measured by differential phosphate analysis. Two tubes are required for each analysis—one for the assay of orthophosphate and another for the determination of the sum of orthophosphate and carbamyl phosphate (after hydrolytic decomposition of the latter). In orthophosphate assay Fiske and SubbaRow reagents are used, and the minor modifications made in the conventional procedure are designed to avoid hydrolysis of carbamyl phosphate during the determination. For protein precipitation, ice-cold TCA is used and the protein precipitate is centrifuged down in chilled metal cups or in a refrigerated centrifuge. Carbamyl phosphate can be hydrolyzed to yield orthophosphate by heating in a boiling water bath for 2 minutes or by exposure to 0.1 N base for 10 minutes at room temperature. 10 The heat treatment is more rapid and may be preferred when there are no other heat-unstable phosphates in the sample.