Arginine is an important substrate in health and disease. It is a commonly held view that arginase-1 release from injured erythrocytes and hepatocytes leads to arginine breakdown; however, the true relationship between plasma arginase-1 concentration and activity has remained unaddressed. In the present study, blood was sampled from patients undergoing liver resection, a known cause of hepatocy...

The control of polyamine synthesis in neoplastic cells is complex and incompletely understood. Using murine lymphoma cells deficient in methylthioadenosine (MTA) phosphorylase, we have analyzed the role of MTA in the regulation of ornithine decarboxylase and S-adenosylmethionine (SAM) decarboxylase, the two rate-limiting enzymes in the polyamine-biosynthetic pathway. The addition of MTA to the ...

The potential for a considerable formation of ornithine exists in lactating mammary gland because of its arginase content. Late in lactation arginase reaches an activity in the gland higher than that present in any rat tissue except liver. Occurrence of the urea cycle can be excluded since two enzymes for the further reaction of ornithine in the cycle, carbamoyl phosphate synthetase I and ornit...

The mitochondrial matrix enzyme, ornithine aminotransferase, is induced in rat liver by the administration of a diet high in protein and by glucagon. The rate of synthesis of the enzyme is increased 100-fold in the livers of rats maintained on a 60% relative to a 0% protein diet, whereas the levels of functional and hybridizable mRNA measured by in vitro translation and through the use of a clo...

Enzymes in the transcarbamylase family catalyze the transfer of a carbamyl group from carbamyl phosphate (CP) to an amino group of a second substrate. The two best-characterized members, aspartate transcarbamylase (ATCase) and ornithine transcarbamylase (OTCase), are present in most organisms from bacteria to humans. Recently, structures of four new transcarbamylase members, N-acetyl-L-ornithin...

Lactobacillus sake isolated from meat can hydrolyze arginine via the arginine deiminase pathway. Two enzymes, arginine deiminase and ornithine transcarbamylase, have been revealed by detection of their reaction products, citrulline and ornithine, respectively. The production of citrulline depends on the concentration of glucose in a synthetic medium; it does not occur when the concentration of ...

1,4-Diaminobutanone, a competitive inhibitor of ornithine decarboxylase in Aspergillus nidulans, is able to increase the half-life of this enzyme and thus stimulate an increase in its activity in vivo. It also protects ornithine decarboxylase against proteolysis by chymotrypsin in vitro.

1. The rate of gluconeogenesis from alanine in the perfused rat liver is affected by the presence of other metabolizable substances, especially fatty acids, ornithine and ethanol. Gluconeogenesis is accelerated by oleate and by ornithine. When both oleate and ornithine were present the acceleration was greater than expected on the basis of mere additive effects. 2. Much NH(3) and some urea were...