Ornithine

	Email		Print
	Bookmark		Link

Ornithine

Ornithine is an amino acid

Amino acid

In chemistry, an amino acid is a molecule containing both amine and carboxyl functional groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent....
which plays a role in the urea cycle

Urea cycle

The urea cycle is a cycle of biochemistry reactions occurring in many animals that produces urea 2carbonoxygen from ammonia . This cycle was the first metabolic cycle discovered ....
.

ll>L-Ornithine is one of the products of the action of the enzyme arginase

Arginase

Arginase is a manganese-containing enzyme. The reaction catalyzed by this enzyme is: arginine + Water ? ornithine + urea. It is the final enzyme of the urea cycle....
on L-arginine

Arginine

Arginine is an a-amino acid. The Optical isomerism is one of the 20 most common natural amino acids. Its codons are CGU, CGC, CGA, CGG, AGA, and AGG....
, creating urea

Urea

Urea is an organic compound with the chemical formula 2carbonoxygen.Urea is also known by the International Nonproprietary Name carbamide, as established by the World Health Organization....
. Therefore, ornithine is a central part of the urea cycle, which allows for the disposal of excess nitrogen

Nitrogen

Nitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674?. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere....
.

Ornithine is not an amino acid coded for by DNA

DNA

Deoxyribonucleic acid is a nucleic acid that contains the genetics instructions used in the development and functioning of all known living organisms and some viruses....
, and, in that sense, is not involved in protein synthesis

Protein biosynthesis

Discussion

Ask a question about 'Ornithine'

Start a new discussion about 'Ornithine'

Answer questions from other users

Full Discussion Forum

Encyclopedia

Ornithine is an amino acid

Amino acid

Urea cycle

The urea cycle is a cycle of biochemistry reactions occurring in many animals that produces urea 2carbonoxygen from ammonia . This cycle was the first metabolic cycle discovered ....
.

Role in urea cycle

L-Ornithine is one of the products of the action of the enzyme arginase

Arginase

Arginase is a manganese-containing enzyme. The reaction catalyzed by this enzyme is: arginine + Water ? ornithine + urea. It is the final enzyme of the urea cycle....
on L-arginine

Arginine

Arginine is an a-amino acid. The Optical isomerism is one of the 20 most common natural amino acids. Its codons are CGU, CGC, CGA, CGG, AGA, and AGG....
, creating urea

Urea

Nitrogen

DNA

Protein biosynthesis

Protein synthesis is the process in which cell build proteins. The term is sometimes used to refer only to protein translation but more often it refers to a multi-step process, beginning with amino acid synthesis and transcription which are then used for translation ....
. However, in mammalian non-hepatic tissues, the main use of the urea cycle is in arginine biosynthesis, so as an intermediate in metabolic processes, ornithine is quite important. ???

Lactamization

It is believed to not be a part of genetic code because polypeptides containing unprotected ornithines undergo spontaneous lactamization. This proved to be a problem when ornithine was artificially incorporated in 21st amino acid systems.

Other reactions

Ornithine, via the action of ornithine decarboxylase

Ornithine decarboxylase

The enzyme ornithine decarboxylase participates in the urea cycle, and in the metabolism of glutathione and amino groups. In humans, this protein has 461 amino acids and forms a homodimer....
(E.C. 4.1.1.17), is the starting point for the synthesis of polyamine

Polyamine

The polyamines are organic compounds having two or more primary amino groups - such as putrescine, cadaverine, spermidine, and spermine - that are essential molecules in both eukaryotic and prokaryotic cells....
s such as putrescine

Putrescine

Putrescine is an organic chemical compound NitrogenHydrogen24NH2 . It is related to cadaverine; both are produced by the breakdown of amino acids in living and dead organisms and both are toxic in large doses....
.

In bacteria, such as E. coli
Escherichia coli

'Escherichia coli' , is a Gram negative bacterium that is commonly found in the lower gastrointestinal tract of warm-blooded animals. Most E....
, ornithine can be synthesized from L-glutamate

Glutamic acid

Glutamic acid is one of the 20 proteinogenic amino acids and its codons are GAA and GAG. It is a non-essential amino acid. The carboxylate anions and salt of glutamic acid are known as glutamates....
.