2-Oxobutanoic acid (alpha-Ketobutyric acid) is a product in the enzymatic cleavage of cystathionine. 2-Oxobutanoic acid is a substance that is involved in the metabolism of many amino acids as well as propanoate metabolism and C-5 branched dibasic acid metabolism. 2-Oxobutanoic acid is also one of the degradation products of threonine. It can be converted into propionyl-CoA (and subsequently methylmalonyl CoA, which can be converted into succinyl CoA, a citric acid cycle intermediate), and thus enter the citric acid cycle.