In eukaryotic cells, the non-proteinogenic amino acid ornithine is the precursor of arginine and polyamines (PAs). The final step of ornithine biosynthesis occurs in plants via a cyclic pathway catalyzed by N(2)-acetylornithine:N-acetylglutamate acetyltransferase (NAOGAcT). An alternative route for ornithine formation, the linear pathway, has been reported for enteric bacteria and a few other o...

We have previously shown that arginine deficiency is exacerbated by the removal of dietary proline in orally, but not parenterally, fed piglets. Therefore, we hypothesized that the net interconversions of proline, ornithine, and arginine primarily occur in the small intestine of neonatal piglets. Ten intragastrically fed piglets received either intraportal (IP) or intragastric (IG) primed, cons...

Ornithine induced more than 36-fold the ornithine decarboxylase activity in confined Ehrlich ascites tumour cells after 3.5 h of continuous perifusion with 0.5 mM ornithine; arginine and glutamine also induced the activity 3- and 4-fold, respectively. The addition of cycloheximide or actinomycin D antibiotics to the perifusion medium confirmed that the regulation of the enzyme synthesis takes p...

Glutamine-dependent carbamyl phosphate synthetase from Escherichia coli can exist in two different conformations which exhibit, respectively, monomer sedimentation coefficients (.&J of 7.3 S and 8.7 S. Both conformations undergo rapid reversible self-association upon addition of potassium ions or ornithine. Formation of the 8.7 S conformation is promoted by the addition of phosphate ions. Low c...

All metazoan cells in culture require either arginine or citrulline for growth (1, 2). The importance of arginine is emphasized by the fact that it is rapidly depleted from the medium in many primary and established cell strains (3). The L-929 fibroblasts maintained in this laboratory and shown to harbor a pleuropneumonia-like infection also demonstrate a.n elevated requirement for this amino a...

The increase in ODC activity during perifusion of Ehrlich carcinoma cells with 0.5 mM ornithine correlates with an increase in 'de novo' synthetized ODC protein. ODC synthesis was followed by immunoprecipitation of equal quantities of 35S-labelled proteins after 10, 20 and 30 min of labelling. In addition, the rate of 'de novo' protein synthesis is very much elevated in cells perifused with sal...

The free amino acid profile of the fruiting bodies of Pleurotus ostreatus was studied in detail. The first evidence for the occurrence of N delta-acetyl-L-ornithine in the mushroom was presented, and 33 ninhydrin-positive compounds were determined, besides N delta-acetyl-L-ornithine. Alanine, glutamic acid, valine, glutamine, glycine and leucine were predominant protein amino acids occurring in...