Metabolism of arginine
1. The metabolic pathway of arginine in the body is to synthesize substances such as urea, ornithine, proline, polyamine, glutamic acid and glutamate through arginase. These substances play important nutritional and physiological functions in the processes of human lactation, growth, development and tissue remodeling. Arginine can also generate ornithine and creatine acetate through the arginine/glycine transaminase way, and the latter can be methylated in the liver to form creatine, which is an important source of creatine in the body.
The immunomodulatory effect of arginine in the body is mainly through two metabolic pathways: the "arginase" pathway and the "NO" pathway.
2. Mammalian arginase, including arginase I and arginase II, both catalyze the conversion of arginine to ornithine and urea.
Arginase I is highly expressed in hepatocytes, and arginase II is a mitochondrial enzyme mainly expressed in kidney, brain, breast, and macrophages. Arginine is converted to ornithine by arginase. Ornithine is the precursor of urea and polyamine, and plays an important role in the urea cycle and the formation of polyamine.
3. As a precursor of nitric oxide, arginine is converted into NO and citrulline under the action of nitric oxide syntheses (NOS) in human body. NO can maintain vascular tone, regulate immunity, and reduce gastrointestinal It plays a role in the damage of the tract mucosa.
Arginine has a secretory effect on a variety of endocrine glands, can promote the secretion of pituitary growth hormone and prolactin, and promote the secretion of insulin, somatostatin, pancreatic polypeptide, etc. from the pancreas, thereby exerting an indirect immune regulation effect.
Arginine is not only a conditionally essential amino acid, but more importantly, it has immune-enhancing and opsonizing effects. Arginine plays an important role in protein anabolism, polyamine and nitric oxide synthesis, and these products are closely related to the body's immune function. Therefore, the application of arginine has received extensive attention in the study of immune nutrition.