arginines

Arginines, in common biochemical usage, refers to arginine, a basic amino acid with a positively charged guanidino group at physiological pH. The biologically active form in humans is L-arginine; D-arginine is much less common in human metabolism. Arginine is a standard component of body proteins and serves as a precursor for several important molecules.

In humans, arginine is both dietarily supplied and endogenously synthesized. It is considered a conditionally essential amino acid: typically nonessential for healthy adults, but required in greater amounts during infancy, illness, trauma, or rapid growth. It is produced mainly in the kidneys and also participates in the urea cycle in the liver, where it is formed from citrulline and subsequently hydrolyzed by arginase into urea and ornithine.

Arginine has several key biological roles. It is the substrate for nitric oxide synthase, producing nitric oxide, a signaling molecule that regulates blood vessel dilation and blood flow. It also contributes to the synthesis of polyamines, which are important for cell growth and wound healing, and to creatine synthesis, which supports energy storage in muscle. Additionally, arginine is involved in various metabolic pathways that support immune function and hormonal regulation.

Dietary sources include meat, fish, dairy products, nuts, seeds, and certain legumes and grains. Arginine supplements are marketed for various conditions, but clinical evidence is mixed, and use should consider potential effects in individuals with kidney disease, urea cycle disorders, or certain viral infections.