Aspartic acid

Aspartic acid is an amino acid. It's one of the amino acids that the body is capable of producing itself, meaning it's unnecessary to find it in dietary sources. However, it's found in quantity in many foods such as oysters, wild game, processed meats, sprouts, and avocados.
As well as being used to build certain proteins, it's also involved in the cycle that changes ammonia to urea.
It's commonly manufactured for use in making other chemicals, such as fertilizers and the artificial sweetener aspartame.
Aspartic acid at Wikipedia