Arginine

Arginine is an essential amino acid found in proteins and is one of three amino acids categorized as basic amino acids. The basic amino acids are strongly polar, and as a consequence, they are usually found on the exterior surfaces of proteins, where they can be hydrated by the surrounding aqueous environment.

Arginine is an intermediate in the urea cycle - Figure 20.14 (reactions 1-2 shown below).

Arginine is a precursor to nitric oxide. In this unusual reaction, an unprecedented five-electron oxidation of arginine occurs (reaction #3 below).

In muscle, arginine is also involved as a precursor of creatine and creatine phosphate (Reaction #4 below).

Arginine is classified as an essential amino acid in mammals, meaning it must be present in the diet.

One Letter Code | Three Letter Code | Molecular Wt. (Daltons) | Genetic Code Codons
R | ARG | 156.20 | CGU, CGC, CGA, CGG, AGA, AGG

Arginine is both metabolically degraded to and synthesized from glutamate through ornithine.

1. Argininosuccinate <=> Arginine + Fumarate (catalyzed by Argininosuccinase).

2. Arginine + H 2O <=> Urea + Ornithine (catalyzed by Arginase)

3. Arginine + O 2 -> Citrulline + Nitric Oxide (catalyzed by Nitric Oxide Synthase).

4. Arginine + Glycine <=> Guanidinoacetate + Ornithine

See also: Table 5.1, Genetic Code, Urea, Ornithine, Citrulline, Glycine, Creatine, Creatine Phosphate, Metabolism of Ornithine and Arginine, Essential Amino Acids

INTERNET LINKS:

> 1. Arginine Metabolism

> 2. Urea Cycle and Metabolism of Amino Groups