Conversion of carbamoyl phosphate to hydroxyurea. An assay for carbamoylphosphate synthetase

A specific colorimetric method for determination of hydroxyurea is described. Using this method it was shown that carbamoyl phosphate or cyanate (a decomposition product of carbamoyl phosphate) and hydroxylamine react to form hydroxyurea. Hydroxylamine was employed to trap carbamoyl phosphate produced by carbamoylphosphate synthetase. A radio chemical assay for activity of carbamoylphosphate synthetase gives results in agreement with the method based on coupling the formation of carbamoyl phosphate with ornithine transcarbamoylase. This new assay is sensitive, rapid, and reproducible, and does not require supplementary enzymes or their substrates in the incubation medium.