Comparative Study on the Mechanism of Photoinduced Electron Transfer from Tryptophan 168 to Excited Flavin in T169S and Wild-type Pyranose 2-Oxidase

Abstract

The rates of photoinduced electron transfer (ET) from Trp168 to the excited isoalloxazine (Iso*) in the pyranose 2-oxidase (P2O) with T169S mutation were studied using ET theory by fitting structural properties calculated from molecular dynamics simulation to the reported fluorescence lifetimes. The obtained ET rates and related physical quantities were compared to those reported for the wild-type (WT) P2O. Experimental fluorescence lifetimes of Iso in T169S have two components of 92–240 fs (depending on the emission wavelength) and 15 ps (independent of the emission wavelength). One of the four T169S subunits (Sub C) displayed a low rate, and the other three (Sub A, B, and D) had high rates. Mean ET rates of the fast components were ca. 10 ps–1 at 480 nm, 7 ps–1 at 500 nm, and 4.2 ps–1 at 530, 555, and 580 nm, which were lower than the reported rates in the WT P2O of ca. 17 ps–1 at 480 nm, 14 ps–1 at 500 nm, 9 ps–1 at 530 and 555 nm, and 11 ps–1 at 580 nm, while the rate for the slow component in T169S (...