Arginine is a semi-essential amino acid which can be synthesized from L-citrulline through the enzymes argininosuccinate synthetase and argininosuccinate lyase.

In mammalian cells, catabolization of arginine may occur by four sets of enzymes:

- aginine:glycine amidinotransferase,
- arginase,
- nitric oxide synthases (NOS),
- arginine decarboxylase

giving rise to ornithine, urea, creatine, citrulline, glutamate, proline, polyamines, nitric oxide (NO) and agmatine.

Metabolic scheme about synthesis and catabolization of arginine

Arginine-derived NO influences tumor initiation, promotion, progression, apoptosis, angiogenesis, differentiation, chemosensitivity, radiosensitivity, and tumor-induced immuno-suppression.

Microbes, furthermore are able to degrade arginine to citrulline and ammonia catabolized by arginine deiminase.

In cell culture deprivation of arginine has been shown to cause cell death of up to 80 % of cancer cell lines.

Addition of citrulline or argininosuccinate into the cultivation medium may circumvent the arginine deficiency.

However, some human cancers, such as melanoma and hepatocellular carcinomas are unable to synthesize arginine from citrulline due to a lack of argininosuccinate synthetase.

References

Nutrients: main page