The rates of oxidation of arginine and ornithine that occurred through a reaction pathway involving the enzyme ornithine aminotransferase (EC 2.6.1.13) were determined using (14)C-labeled amino acids in the isolated nonrecirculating perfused rat liver. At physiological concentrations of these amino acids, their catabolism is subject to chronic regulation by the level of protein consumed in the ...

In extracts from the youngest leaves of Avena sativa, Hordeum vulgare, Zea Mays, Pisum sativum, Phaseolus vulgaris, Lactuca sativa, and four pyrrolizidine alkaloid-bearing species of Heliotropium, the activities of ornithine decarboxylase, close to V(max), ranged between traces and 1.5 nanomoles per hour per gram fresh weight when based on putrescine formed during incubation with labeled ornith...

The proposed structure of the ornithine-containing lipid of Bordetella pertussis is 3-hydroxyhexadecanoic acid amide-linked to ornithine and esterified to the second hexadecanoic acid. The aminolipid strongly agglutinates type A and B human erythrocytes.

mammalian ∆-(1)-pyrroline-5-carboxylate synthase (p5cs) enzyme catalyzes the coupled phosphorylation and reduction-conversion of glutamate to ∆-(1)-pyrroline-5-carboxylate (p5c), a critical step in the proline, ornithine, citrulline and arginine biosynthesis. in plants and mammals, p5cs consists of two separate enzymatic domains: n-terminal γ-glutamyl kinase (γ-gk) and c-terminal γ-glutamyl pho...

We hypothesized recently that arginine homeostasis is achieved in humans largely by modulating the rate of arginine degradation. We have tested this hypothesis further by measuring in vivo the whole body rate of conversion of arginine to ornithine and ornithine oxidation in six healthy young adults. Subjects received for 6 days an L-amino acid-based diet supplying an arginine-rich or arginine-f...

Previous studies of serine dehydratase (EC 4.2.1.13) and ornithine aminotransferase (EC 2.6.1.13) adaptation in rat liver showed that in rats on a high protein diet, glucocorticoid administration increased serine dehydratase activity while simultaneously reducing the activity of ornithine aminotransferase. The present study examines the role of enzyme synthesis in the expression of these and ot...

The activity and stability of L-ornithine decarboxylase from rat ventral prostate is markedly increased by certain thiol compounds, notably dithiothreitol. The enzyme was purified about 300-fold. Many properties of the purified enzyme are described. In the absence of added thiol compounds, the purified ornithine decarboxylase apparently undergoes polymerization, as evidenced by its behavior on ...

The transport activity of arginine in mouse peritoneal macrophages was strongly induced when they were cultured with 1 ng/ml bacterial lipopolysaccharide (LPS) for 12 h. Arginine in the medium decreased whereas ornithine in the medium increased during the culture. This time-dependent change of arginine to ornithine was accelerated by LPS. However, the activity of arginase in the macrophages did...

The plant oncogene rolD stimulates the reproductive phase transition in plants. We define here the function of its gene product. We show that the RolD protein bears sequence homology with ornithine cyclodeaminase, an uncommon enzyme of specialized-niche eubacteria and archaea that catalyzes the unusual NAD(+)-dependent conversion of ornithine to proline. To confirm the prediction of the bioinfo...