Aspartic acid is a nonessential amino acid that plays roles in many important metabolic processes, such as energy production (citric acid cycle), hormone metabolism, CNS activation, and the urea cycle. It is found in many protein sources such as oysters, meats, seeds, avocado, asparagus, and beets.

It is also an ingredient in artificial sweeteners.

Aspartic acid is a precursor to many amino acids and other molecules like asparagine, arginine, isoleucine, lysine, methionine, isoleucine, threonine, nucleotides, NAD, and pantothenate. Aspartate, like glutamine, can also be considered a neuroexcitatory neurotransmitter since it activates the N-methyl-D-aspartate receptor in the brain.

Aspartate transaminase (AST) is an enzyme that catalyzes the transfer of an amino group from L-aspartate to alpha-keto glutarate. This reaction serves as a cellular energy source and takes place mainly in the liver, skeletal muscle, myocardium, and kidneys.

Although AST is commonly measured on traditional laboratory profiles as a measure of liver dysfunction and muscle injury, it is not specific enough to be used alone as a diagnostic tool.