In this paper, we show that the L-enantiospecific hydrolysis of D,L-alpha-aminonitriles into L-alpha-amino acids is catalyzed by an amidase (pronase) immobilized on poly(N-acryloylpiperidin-4-one). Actually, the support chemically participates in the catalytic action since the ketonic sites (piperidin-4-one) catalyze the D,L-alpha-aminonitrile hydration into D,L-alpha-aminoamide in a medium specifically buffered by berates or phosphates at pH 10-11. These conditions are compatible with the enzymatic activity of the pronase and allow the simultaneous transformation of the D,L-alpha-aminoamide formed in the resin into the corresponding L-alpha-amino acid.