Mainly microorganisms but only a few higher organisms are presently known to express enzymes that hydrolyze peptides containing d-amino acids. These enzymes can be involved in proceedings at the bacterial cell wall, in either assembly or modification, and thus cause resistance to glycopeptide antibiotics, or mediate resistance against β-lactam antibiotics. In other cases the in vivo function is still unknown. New enzymes screened from nature, such as d-aminopeptidase, d-amino amidase, alkaline d-peptidase or d-amino-acylase, offer potential application in the production of d-amino acids, the synthesis of d-amino acid oligomers by promoting the reversed reaction under appropriate conditions, or in the field of semi-synthetic antibiotics.