Abstract
d-Amino acids, enantiomers of corresponding l-amino acids, play various biological roles not only in bacteria but
also in eukaryotes. In mammals, they are synthesized from l-amino acids by the action of amino acid racemase or
derived from dietary foods and intestinal bacterial products, and contribute to significant biological events such as
neurotransmission, hormone biosynthesis, and so on. The main enzyme involved in degradation of d-amino acids in
mammals is d-amino acid oxidase. The enzyme relates to degradation of excess and/or unnecessary d-amino acids
and to production of corresponding 2-keto acids, ammonia, and hydorgenperoxide. The regulation of d-amino acids
level is considered to be quite important for life; however, there are still many unknown aspects. In this minireview,
we summarize the d-amino acids metabolism in mammals.
