ornithine


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ornithine

 [or´nĭ-thēn]
an amino acid obtained from arginine by splitting of urea; it is an intermediate in urea biosynthesis.
ornithine carbamoyltransferase (ornithine transcarbamylase) an enzyme that catalyzes a reaction occurring in the liver mitochondria as part of the urea cycle.

or·ni·thine (Orn),

(ōr'ni-thēn, -thin),
2,5-Diaminovaleric acid; the l-isomer is the amino acid formed when l-arginine is hydrolyzed by arginase; not a constituent of proteins, but an important intermediate in the urea cycle; elevated levels seen in certain defects of the urea cycle.

ornithine

/or·ni·thine/ (or´nĭ-thēn) an amino acid obtained from arginine by splitting of urea; it is an intermediate in urea biosynthesis.

ornithine

(ôr′nə-thēn′)
n.
An amino acid, C5H12N2O2, not found in proteins, formed by hydrolyzing arginine and important in the formation of urea.

ornithine

[ôr′nithēn]
an amino acid, not a constituent of proteins, that is produced as an important intermediate substance in the urea cycle. It is formed by the hydrolization of arginine by arginase and is subsequently converted into citrulline. It decomposes by losing carbon dioxide, producing putrescine and a strong foul odor characteristic of decaying animal tissue. Also called diaminovaleric acid.

or·ni·thine

(ōr'ni-thēn)
The amino acid formed when l-arginine is hydrolyzed by arginase; an important intermediate in the urea cycle; elevated levels seen in certain defects of the urea cycle.

ornithine

dietary supplement which in combination with other amino acids arginine and lysine is claimed to increase muscle growth/lean body mass to a greater extent than strength training alone, but this has not been supported by properly designed trials. See also ergogenic aids; appendix 4.4 .

or·ni·thine

(Orn) (ōr'ni-thēn)
Amino acid formed when l-arginine is hydrolyzed by arginase; important intermediate in the urea cycle.

ornithine (ôr´nəthēn´),

n an amino acid, not a constituent of proteins, that is produced as an important intermediate substance in the urea cycle.
ornithine carbamoyltransferase,
n an enzyme in the blood that increases in patients with liver and other diseases.

ornithine

an amino acid obtained from arginine by the action of the enzyme arginase which also splits off urea; it is an intermediate in urea biosynthesis.

ornithine carbamoyl transferase (OCT), ornithine transcarbamoylase
see ornithine carbamoyl transferase.
ornithine cycle
alternative name for urea cycle since ornithine is the carrier of the nitrogens.
ornithine decarboxylase test
a means of identifying different members of the Enterobacteriaceae as well as other gram-negative bacteria.
ornithine-δaminotransferase
deficiency see gyrate atrophy.
References in periodicals archive ?
Much more arginine may be used in the ornithine production and this may lead to formation of polyamines which have been previously shown to be closely related to cancer progression.
2) This is demonstrated by the inability to find any mutations in 20% of the ornithine transcarbamylase deficiency carriers.
Co-operation between follicular ornithine decarboxylase and v-Haras induces spontaneous papillomas and malignant conversion in transgenic skin.
1990) demonstrated that the endogenous synthesis of Arg in the kidney depends on the synthesis of ornithine and citrulline in the intestine.
Concentrations of arginine, citrulline and ornithine in plasma were influenced by oxidative stress (Table 5).
The ornithine synthesized by arginase could also act through other pathways in the pancreatic islets, besides the production of polyamines, as it has been proven in isolated islets that ornithine has a positive effect on insulin secretion and that a-difluoromethylornithine, a specific inhibitor of ornithine decarboxylase, the enzyme that turns ornithine into putrescine, does not block its insulin secretagogue action [55].
Through weight management, exercise, healthy sleep habits, minimizing intake of high-glycemic-load carbohydrates, and consuming targeted nutrients such as CDP-choline, niacin, glycine, glutamine, arginine, and ornithine, you may safely and cost-effectively capture the many benefits of naturally high GH levels.
The [alpha]-difluormethylornithine ([alpha]-DFMO), which is the ornithine decarboxylase suicide inhibitor, has been extensively used to study the effects of limiting polyamine synthesis in cell culture and in experimental animals (Poso and Pegg, 1982; Pegg, 1986; Grossie et al.
Gerner of the University of Arizona, Tucson, to fight the development of cancer by targeting ornithine decarboxylase, a key polyamine pathway that acts as an instigator of growth.
It is also of interest to note that the levels of ornithine, Pu precursor amino acid, decreased significantly at days 10 and 17 of lymphoma growth, compared to basal levels, and then increased at day 24 when mice were in terminal stages (Figure 3c).
In particular, for ameliorating the symptoms or onset of amyotrophic lateral sclerosis (ALS) by modulating the gene and protein products involved the polyamine pathway, such as by inhibiting the enzyme, ornithine decarboxylase (ODC), involved in the synthesis of the polyamine, putrescine.
beverage called Office Diet, formulated with carnitine, ornithine and