Aspartic acid also called aspartate with symbol D or Asp, is an α-amino acid which is used in protein biosynthesis. Alike other amino acids, it contain an amino group and carboxylic acid. The amino group is in protonated –NH+3 form under physiological conditions. It has acidic side chain (CH2COOH) which reacts with other amino acids, proteins and enzymes in the body. The side chain in proteins occurs as negatively charged aspartate form −COO− under physiological conditions. In humans, it is a non-essential amino acid which refers that body could synthesize it as required. It is encoded by all codons GAC and GAU.

L-isomer of Asp is one of 22 proteinogenic amino acids which is building blocks of proteins. Aspartic acid is regarded as acidic amino acid having pKa of 3.9 yet it is highly dependent on local environment and could be high as 14. Asp is pervasive in biosynthesis. This nonessential amino acid is made from glutamic acid by enzymes with use of Vitamin B6. Aspartic acid has valuable roles in urea cycle as well as DNA metabolism. It is a major excitatory neurotransmitter which is increased in stroke and epileptic patients. It is diminished in depressed patients and patients having brain atrophy.

It is pervasive in biosynthesis and a precursor to various amino acids. It is a metabolite in urea cycle and engages in gluconeogenesis. It also performs as neurotransmitter.

Discovery

In 1827, aspartic acid was discovered by Étienne Ossian Henry and Auguste-Arthur Plisson by hydrolysis of asparagine which was isolated in 1806 from asparagus juice. The original method used lead hydroxide but other acids or bases are also commonly used instead.

Health Benefits of Aspartic acid

Let’s discover the health benefits of aspartic acid:

Increase testosterone levels

Study has shown that D-Asp supplements enhance testosterone levels in male animals. Yet scientific evidence is weaker, less consistent and scarier. 12 day study shows that intake of 3.12 grams of D-Asp regularly enhanced testosterone levels in men. Study shows that taking 6 grams of D-Asp daily lowers testosterone. Supplementation of D-Asp increases testosterone levels in healthy, nonresistance training men for shorter time periods. Still study is required for verifying these results.

Promote sperm quality

D-Asp rich foods or D-Asp supplements promotes male fertility. In male animals, D-Asp formed by body promotes testosterone and other sex hormones. Literally, D-Asp controls development of healthy sperm required for reproduction. In animals, supplemental and naturally produced D-Asp enhance fertility or sperm quality. Human study also shows similar trends. Food supplements with D-Asp increased sperm counts as well as sperm swimming abilities. Supplements of D-Asp are helpful for people with infertility problems.

Female fertility

In-vitro fertilization clinics explore new and more efficient or reliable ways for determining and increasing quality of egg cells in prospective mothers. Such method lowers number of fertilized embryos needed for successful pregnancy. It also lowers the need for storing embryos for longer time period. The quality of egg could be affected by D-Asp occurring naturally in follicular fluid which surrounds, nourishes and protects egg cells in ovaries. It promotes egg quality by influencing growth hormone, estrogen, prolactin, amino acids, nitric acid, progesterone and proteins.

Enhance memory

Mice studies shows that D-Asp promote brain cell communication and memory. Human study concluded increase level of enzyme alter many D-amino acids that promotes memory and thought process. D-amino acids adjust by DAO act similar to D-Asp. It is possible that D-Asp act as naturally occurring nootropic.

Dietary sources

Food name	Weight (g)	Aspartic acid (g)
Turkey	863	24
Egg white	107	9
Soybeans	186	9
Lupins	180	6
Spirulina	112	6
Mungo beans	207	6
Hyacinth beans	210	5
Winged beans	182	5
Kidney beans	184	5
Black beans	194	5
Adzuki beans	197	4
Almonds	143	3
Kielbasa	370	3
Tilefish	150	3
Butternuts	120	3
Natto	175	3
Tempeh	166	3
Pork	135	3
Ocean pout	137	2
Wolffish	119	2