| dc.description.abstract | According to our earlier study in cytochrome P450 BM3, for the oxidation of simple aromatics, we chose to mutate its amino acid residue at position 328 from alanine to
phenylalanine. The catalytic efficiency (turn over frequencies (TOF)) of toluene and benzene, mediated by this specific mutant, for the phenol and cresols production, can be increased 2.5 to 4 times higher than the wild-type strain. On the other hand, in the case of another cytochrome P450 BM3 variant, A74G F87V L188Q, except to the formation of o-cresol of toluene oxidation at sp2 position, one additional product of benzyl alcohol for sp3-selective product was observed and its ratio is 27%. Introducing one additional mutation site of A328F can enhance the sp3 product selectivity ratio up to 50%.
A biomimetic system of cytochrome P450 BM3 for the oxidation of benzene and toluene catalyzed by iron(II) perchlorate using H2O2(aq) in CH3CN was also undertaken in this study. The reactions can be facilely tuned and controlled to selectively yield either a single or double oxygenation of benzene as well as a sp3 or sp2 C–H bond oxidation of toluene.
In order to further delineate the reaction mechanisms of the oxy-functionalization at the sp3 and/or sp2 centers, for the comparison between cytochrome P450 BM3 and its
biomimetic system of Fe(ClO4)2 in an H2O2-H2O-CH3CN system, we conducted studies that included measurements of kinetic isotope effects (KIEs) by mixing C6D6 with C6H6 or C7D8 with C7H8, each in a 1:1 ratio. Our data reveal that both of the KIE data in benzene oxidations presented an inverse secondary KIE manner and, in the
case of toluene oxidation, the KIE for cytochrome P450 BM3 was also performed as Inverse secondary kinetic isotope effect (0.7-1.0). However, KIE for Fe(ClO4)2
biomimetics on the contrary was appeared as normal secondary kinetic isotope effect. | en_US |