Human carbamoylphosphate synthetase I.

Carbamoylphosphate synthetase (ammonia) isolated from human liver has been characterized. It is composed of monomers (constituted by a single polypeptide of 160,000 +/- 5,000 Mr) that can associate into dimers, although in the native state the monomer predominates. Physical and kinetic properties and amino acid composition are very similar to those found for the rat liver enzyme. There is extensive immunological cross-reactivity between the enzymes from both species. These results are discussed in the light of a possible regulatory role of carbamoylphosphate synthetase. The implications of these findings on a number of pathological states are also discussed.