The invention concerns novel polypeptides and their fragments, isolated from Lactobacillus, having at least a N-deoxyribosyl transferase activity, the polynucleotides encoding said polypeptides, cloning and/or expression vectors including said polynucleotides, cells transformed by said vectors and specific antibodies directed against said polypeptides. The invention also concerns a method for enzymatic synthesis of deoxyribonucleosides.