Ambert-Balay K, Dougherty M, Tien M
Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park 16802, USA.
Arch Biochem Biophys. 2000 Oct 1;382(1):89-94. doi: 10.1006/abbi.2000.2000.
The purpose of this study was to determine the effect of heme pocket hydrophobicity on the reactivity of manganese peroxidase. Residues within 5 A of the heme active site were identified. From this group, Leu169 and Ser172 were selected and mutated to Phe and Ala, respectively. The mutant proteins were then characterized by steady-state kinetics. Whereas the Leu169Phe mutation had little, if any, effect on activity, the Ser172Ala mutation decreased kcat and also the specificity constant (kcat/Km) for Mn2+, but not H2O2. Transient-state studies indicated that the mutation affected only the reactions of compound II. These results indicate that compound II is the most sensitive to changes in the heme environment.
