The present thesis describes the mechanism of the Candida antarctica lipase B (CALB) catalyzed ring-opening polymerization of -lactam and -caprolactone, which has been elucidated by molecular modeling techniques. In contrast to polyesters, polyamides are not yet accessible via lipase catalyzed polymerization. While polyesters are readily accessible by enzymatic polymerization from the corresponding lactones, -lactam up to now is the only amide that has been polymerized using CALB. The reaction, however, results in nylon 3, with only a maximum chain length of 18 and an average length of 8 monomer units. With this background, the aim of this thesis was a comparative study of mechanistic details of the CALB-catalyzed polymerization of lactams and lactones particularly using -lactam and -caprolactone as the most prominent example of a lactone polymerization yielding a polymer of high molecular weight. The basic steps of the CALB-catalyzed polymerization of -lactam and -caprolactone were investigated with atomistic details based on experimental data by applying molecular modeling techniques like docking, molecular dynamics and QM/MM-procedures. The reaction sequence is initiated by covalent binding of the monomers yielding a tetrahedral intermediate TI1, which is ring-opened to an acyl enzyme complex. In contrast to the lactone polymerization, the inverse TI1 of the lactam mechanism utilizes a water molecule as proton shuttle in this step. Release of the acyl chain from the enzyme by hydrolytic cleavage, which permanently competes with chain elongation, causes liberation of the corresponding acids -alanine and 6-hydroxyhexanoic acid, respectively. -alanine featuring a higher acidity is able to inhibit the enzyme irreversibly. Chain elongation proceeds via an activated monomer, which is formed by addition of a catalytic water molecule to the monomer.