A direct method for the estimation of ornithine carbamoyltransferase activity in serum

Ornithine carbamoyltransferase (EC 2.1.3.3) activity was estimated by determining the amount of citrulline produced. The citrulline was colorimetrically measured by using a diacetylmonoxime-thiosemicarbazide reaction without deproteinization. The color complex which had the maximum absorbance at 515 nm was stable at room temperature in daylight for at least several hours. The proposed method was superior to other methods already reported in sensitivity, stability and simplicity.