Molecular origin of rapid versus slow intramolecular electron transfer in the catalytic cycle of the multicopper oxidases.

ABSTRACT: Kinetic measurements on single-turnover processes in laccase established fast type-1 Cu to trinuclear Cu cluster (TNC) intramolecular electron transfer (IET) in the reduction of the native intermediate (NI), the fully oxidized form of the enzyme formed immediately after O-O bond cleavage in the mechanism of O2 reduction. Alternatively, slow IET kinetics was observed in the reduction of the resting enzyme, which involves proton-coupled electron transfer on the basis of isotope measurements. The >10(3) difference between the IET rates for these two processes confirms that the NI, rather than the resting enzyme that has been defined by crystallography, is the fully oxidized form of the TNC in catalytic turnover. Computational modeling showed that reduction of NI is fast because of the larger

SUBMITTER: Heppner DE 

PROVIDER: S-EPMC3807568 | biostudies-literature | 2013 Aug

REPOSITORIES: biostudies-literature