Aspartic acid (Asp), also known as aspartate, the name of its anion, is one of the 20 natural proteinogenic amino acids which are the building blocks of proteins.
As with each of the 20 natural amino acids, there are two abbreviations commonly used to designate aspartic acid: Asp (three letter) and D (one letter). The abbreviations signifying a choice of either aspartic acid or asparagine are Asx (three-letter) and B (one letter).()
As its name indicates, aspartic acid is the carboxylic acid analog of asparagine. It is non-essential in mammals, and might serve as an excitatory neurotransmitter in the brain. It is also a metabolite in the urea cycle, and participates in gluconeogenesis.
As a neurotransmitter, aspartic acid may provide resistance to fatigue and thus lead to endurance, although the evidence to support this idea is not strong.