Carnosine

Carnosine is a dipeptide molecule, made up of the amino acids beta-alanine and histidine. It is highly concentrated in muscle and brain tissues. Carnosine was discovered by Russian chemist Vladimir Gulevich.
Carnosine is naturally produced by the body in the liver from beta-alanine and histidine. Like carnitine, carnosine is composed of the root word carn, meaning "flesh", alluding to its prevalence in meat. There are no plant-based sources of carnosine. Carnosine is readily available as a synthetic nutritional supplement.
Carnosine can chelate divalent metal ions. Carnosine is also considered a geroprotectant.
Products containing carnosine are also used in topical preparations to reduce wrinkles on the skin.
Carnosine may increase the Hayflick limit in human fibroblasts, it also appears to reduce the rate of telomere shortening. This could potentially promote the growth of certain cancers that thrive due to telomere preservation.

Biosynthesis

Carnosine is synthesized within the body from beta-alanine and histidine. Beta-alanine is a product of pyrimidine catabolism and histidine is an essential amino acid. Since beta-alanine is the limiting substrate, supplementing just beta-alanine effectively increases the intramuscular concentration of carnosine.

Physiological effects

pH buffer

Carnosine has a pK_a value of 6.83, making it a good buffer for the pH range of animal muscles. Since beta-alanine is not incorporated into proteins, carnosine can be stored at relatively high concentrations. Occurring at 17–25 mmol/kg, carnosine is an important intramuscular buffer, constituting 10–20% of the total buffering capacity in type I and II muscle fibres.

Anti-oxidant

Carnosine has been shown to scavenge reactive oxygen species as well as alpha-beta unsaturated aldehydes formed from peroxidation of cell membrane fatty acids during oxidative stress. It also buffers pH in muscle cells, and acts as a neurotransmitter in the brain. It is also a zwitterion, a neutral molecule with a positive and negative end.

Antiglycating

Carnosine acts as an antiglycating agent, reducing the rate of formation of advanced glycation end-products, and ultimately reducing development of atherosclerotic plaque build-up.

Geroprotective

Carnosine is considered as a geroprotector. Carnosine can increase the Hayflick limit in human fibroblasts, as well as appearing to reduce the telomere shortening rate. Carnosine may also slow aging through its anti-glycating properties.

Other

Carnosine can chelate divalent metal ions. It has been suggested that binding Ca²⁺ may displace protons, thereby providing a link between Ca²⁺ and H⁺ buffering. However, there is still controversy as to how much Ca²⁺ is bound to carnosine under physiological conditions.