Thermodynamic analysis of MauG, a diheme oxygenase
Kim, H.B., Chonnam National University, Gwangju, Republic of Korea | Shin, S., Chonnam National University, Gwangju, Republic of Korea | Choi, M., Seoul National University of Science and Technology, Seoul, Republic of Korea
MauG is a unique c-type diheme oxygenase. One heme of MauG is five-coordinate and solvent accessible with His53 as axial ligand, while the other heme of MauG is six-coordinate with His205 and Tyr294. MauG catalyzes posttranslational modification including oxygen insertion, cross-linkage of two tryptophan and oxidation of quinol to quinone of precursor methylamine dehydrogenase (preMADH) to form mature tryptophan tryptophylquinone (TTQ) which is one of protein-derived cofactors. Longrange remote catalysis of substrate is possible without direct contact between hemes of MauG and its substrate, preMADH. Although catalytic properties and mechanisms of MauG have been well studied, temperature dependence of MauG has never been reported yet. Therefore, the objective of this study was to perform thermodynamic analysis of MauG. DH of 87.6 ± 6.7 kJ mol-¹ and DS of 232 ± 15.6 J mol-¹K-¹ were directly measured for oxidized MauG in this study. Those results provide fundamental information on controlling electron transfer rates for biosynthesis of TTQ in MADH and are used as a good thermodynamic example study for other diheme systems.
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