The elementary steps of the enzymatic oxidation of nifedipine (NF) catalyzed by horseradish peroxidase (HRP) have been described based on analysis of kinetic magnetic field effects (MFEs). It has been shown that the first step of the catalytic cycle is single electron transfer resulting in formation of NF*(+) radical cation and ferroperoxidase (Per(2+)). As a result, comparison with an earlier studied oxidation reaction of NADH catalyzed by HRP evidenced that the enzymatic oxidations of two substrates-native, NADH, and its synthetic analogue, NF-catalyzed by HRP in the absence of H(2)O(2) follow identical mechanisms.