Biosynthesis of Urea

Biosynthesis of Urea

The biosynthesis of arginine from citrulline involves an adenosinetriphosphate-dependent condeusation of citrulline with aspartic acid to form an intermediary condensation product (l-4), and this is followed, in a separate step, by the cleavage of the intermediate to arginine and fumaric acid (5). The new amino acid, only briefly described previously (2, 6), has been prepared biosynthetically o...

Biosynthesis of urea; enzymatic mechanism of arginine synthesis from citrulline.

In urea synthesis, according to the Krebs-Henseleit ornithine cycle (l), the transfer of nitrogen to citrulline to form arginine (Step II) was thought to occur from NH$. It was not until Cohen and Hayano (2) succeeded in demonstrating rapid arginine synthesis in liver homogenates from glutamic acid and citrulline that the transfer from an amino acid rather than from NH, was recognized as a main...

Biosynthesis of urea. XIV. The quaternary structure of argininosuccinase.

The Regulation of Urea-biosynthesis Enzymes in Vertebrates.

1. Carbamoyl phosphate synthetase, ornithine transcarbamoylase, the arginine-synthetase system and arginase were measured in the livers of ammoniotelic, ureotelic and uricotelic animals. The chelonian reptiles, whose nitrogen excretory patterns vary according to the habitat, and the Mexican axolotl, a neotenic species, were also studied. 2. The levels of the activities of the first three enzyme...

Biosynthesis of urea; arginine synthesis from citrulline in liver homogenates.

A preceding paper described the characteristics of the isolated enzyme system, prepared from ox liver acetone powder, which catalyzes the conversion of citrulline and aspartic acid to arginine and malic acid. It was shown that the fundamental requirements for arginine synthesis from citrulline are aspartic acid, Mg++, and adenosine triphosphate (ATP), the latter as a reactant in substrate conce...