The first three steps are catalyzed by CAD,  a trifunctional cytoplasmic enzyme cluster containing carbamylphosphate synthetase, aspartate carbamyltransferase, and dihydroorotase (Fig.
 Nonstandard abbreviations: CAD, carbamylphosphate synthetase-aspartate carbamyltransferase-dihydroorotase; MS/MS, tandem mass spectrometry; IS, internal standard; N-C-aspartate, N-carbamyl-aspartate; and ESI, electrospray ionization.
In an effort to identify the salt-sensitive site(s) in de novo arginine synthesis, we quantified the effect of the salt treatment on the incorporation of [[sup.14]C]citrulline into [Sigma]A + U by intact cells and on the activities of glutamine synthetase (GS) and carbamylphosphate synthetase (CPSase) in cell-free extracts of YFE leaves from salinized and control plants of both species.
Effect of 16 d of salination with 40 mM NaCl plus 20 MM [CaCl.sub.2] on carbamylphosphate synthetase activity in cell-free extracts of YFE leaves of P.
Abbreviations: [Sigma]A + U, total combined pool of arginine plus urea; YFE, young fully expanded; [Sigma]UMP, sum of the uridine nucleotides converted to UMP by acid hydrolysis at 100 [degrees] C; [Psi]s, osmotic potential; CPSase, carbamylphosphate synthetase; CP, carbamylphosphate; GS, glutamine synthetase; OCTase, ornithine carbamyltransferase; ACTase, aspartate carbamyltransferase.
High reactivity of kidney preparations from man, pig, beef, dog and rat for carbamylphosphate hydrolysis.
Carbamylphosphate hydrolysis in rat tissues and tumors by alkaline phosphatase.