Β-Alanine

β-Alanine (beta-alanine) is a naturally occurring beta amino acid, which is an amino acid in which the amino group is attached to the β-carbon (i.e. the carbon two carbon atoms away from the carboxylate group) instead of the more usual α-carbon for alanine (α-alanine). The IUPAC name for β-alanine is 3-aminopropanoic acid. Unlike its counterpart α-alanine, β-alanine has no stereocenter.

β-Alanine

Names
IUPAC name β-Alanine
Systematic IUPAC name 3-Aminopropanoic acid
Other names 3-Aminopropionic acid
Identifiers
CAS Number	107-95-9 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:16958 Y
ChEMBL	ChEMBL297569 Y
ChemSpider	234 Y
DrugBank	DB03107 Y
ECHA InfoCard	100.003.215
EC Number	203-536-5
IUPHAR/BPS	2365
KEGG	D07561 Y
PubChem CID	239
UNII	11P2JDE17B Y
CompTox Dashboard (EPA)	DTXSID0030823
InChI InChI=1S/C3H7NO2/c4-2-1-3(5)6/h1-2,4H2,(H,5,6) Y Key: UCMIRNVEIXFBKS-UHFFFAOYSA-N Y InChI=1/C3H7NO2/c4-2-1-3(5)6/h1-2,4H2,(H,5,6) Key: UCMIRNVEIXFBKS-UHFFFAOYAL
SMILES O=C(O)CCN
Properties[1][2]
Chemical formula	C3H7NO2
Molar mass	89.093 g/mol
Appearance	white bipyramidal crystals
Odor	odorless
Density	1.437 g/cm3 (19 °C)
Melting point	207 °C (405 °F; 480 K) (decomposes)
Solubility in water	54.5 g/100 mL
Solubility	soluble in methanol. Insoluble in diethyl ether, acetone
log P	−3.05
Acidity (pKa)	3.55 (carboxyl; H2O) 10.24 (amino; H2O)[3]
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Irritant
NFPA 704 (fire diamond)	2 1 0
Lethal dose or concentration (LD, LC):
LD50 (median dose)	1000 mg/kg (rat, oral)
Safety data sheet (SDS)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Biosynthesis and industrial route

In terms of its biosynthesis, it is formed by the degradation of dihydrouracil and carnosine. β-Alanine ethyl ester is the ethyl ester which hydrolyses within the body to form β-alanine.^[4] It is produced industrially by the reaction of ammonia with β-propiolactone.^[5]

Sources for β-alanine includes pyrimidine catabolism of cytosine and uracil.

Biochemical function

β-Alanine residues are rare. It is a component of the peptides carnosine and anserine and also of pantothenic acid (vitamin B₅), which itself is a component of coenzyme A. β-alanine is metabolized into acetic acid.

Precursor of carnosine

β-Alanine is the rate-limiting precursor of carnosine, which is to say carnosine levels are limited by the amount of available β-alanine, not histidine.^[6] Supplementation with β-alanine has been shown to increase the concentration of carnosine in muscles, decrease fatigue in athletes, and increase total muscular work done.^[7][8] Simply supplementing with carnosine is not as effective as supplementing with β-alanine alone since carnosine, when taken orally, is broken down during digestion to its components, histidine and β-alanine. Hence, by weight, only about 40% of the dose is available as β-alanine.^[6]

Comparison of β-alanine (right) with the more customary, chiral, α-amino acid, L-α-alanine (left)

Because β-alanine dipeptides are not incorporated into proteins, they can be stored at relatively high concentrations. Occurring at 17–25 mmol/kg (dry muscle),^[9] carnosine (β-alanyl-L-histidine) is an important intramuscular buffer, constituting 10-20% of the total buffering capacity in type I and II muscle fibres. In carnosine, the pK_a of the imidazolium group is 6.83, which is ideal for buffering.^[10]

Receptors

Even though much weaker than glycine (and, thus, with a debated role as a physiological transmitter), β-alanine is an agonist next in activity to the cognate ligand glycine itself, for strychnine-sensitive inhibitory glycine receptors (GlyRs) (the agonist order: glycine ≫ β-alanine > taurine ≫ alanine, L-serine > proline).^[11]

β-alanine has five known receptor sites, including GABA-A, GABA-C a co-agonist site (with glycine) on NMDA receptors, the aforementioned GlyR site, and blockade of GAT protein-mediated glial GABA uptake, making it a putative "small molecule neurotransmitter."^[12]

Athletic performance enhancement

There is evidence that β-alanine supplementation can increase exercise and cognitive performance,^{[13][14][15][16]} for some sporting modalities,^[17] and exercises within a 0.5–10 min time frame.^[18] β-alanine is converted within muscle cells into carnosine, which acts as a buffer for the lactic acid produced during high-intensity exercises, and helps delay the onset of neuromuscular fatigue.^[15][19]

Ingestion of β-alanine can cause paraesthesia, reported as a tingling sensation, in a dose-dependent fashion.^[16] Aside from this, no important adverse effect of β-alanine has been reported, however, there is also no information on the effects of its long-term usage or its safety in combination with other supplements, and caution on its use has been advised.^[13][14] Furthermore, many studies have failed to test for the purity of the supplements used and check for the presence of banned substances.^[15]

Metabolism

β-Alanine can undergo a transamination reaction with pyruvate to form malonate-semialdehyde and L-alanine. The malonate semialdehyde can then be converted into malonate via malonate-semialdehyde dehydrogenase. Malonate is then converted into malonyl-CoA and enter fatty acid biosynthesis.^[20]

Alternatively, β-alanine can be diverted into pantothenic acid and coenzyme A biosynthesis.^[20]