Study of carbamyl phosphate-ornithine transcarbamylase.

The enzyme carbamyl phosphate-ornithine transcarbamylase, which catalyzes the synthesis of citrulline from ornithine plus carbamyl phosphate, has been partially purified from rat liver by means of heat treatment and ethanol fractionation (1). Krebs et al. (2) were able to demonstrate the arsenolysis of citrulline in a number of tissues and, by using sheep liver mitochondria, were able to purify partially the enzyme responsible. These workers proposed that the citrulline-synthesizing system might be responsible for citrulline breakdown. Recent work by Marshall (3) and by Smith and Reichard (4) lends support to this proposal. Conditions for preparing highly purified carbamyl phosphate-ornithine transcarbamylase are reported in the present paper. In addition, some kinetic and other properties of the enzyme system have been investigated.