SPECTROSCOPIC AND FUNCTIONAL-STUDIES OF A NOVEL QUADRUPLE MYOGLOBIN VARIANT WITH INCREASED PEROXIDASE-ACTIVITY

A quadruple variant of horse heart myoglobin (Thr39Ile/Lys45Asp/Phe46L eu/Ile107Phe) that exhibits significantly (similar to 25-fold) greater peroxidase activity than the wild-type protein has been studied to de termine its midpoint reduction potential (24(2) mV vs. SHE; pH 6.0, mu = 0.1M, 25 degrees C) and to characterize the kinetics of its reactio n with hydrogen peroxide, In addition, Fourier transform infrared (FTI R) spectra of the carbonyl and azide adducts of the protein have been obtained to gain initial insight into the effects of these substitutio ns on the ligand binding properties of the reduced and oxidized varian t. All of the results obtained in this work are consistent with a vari ant heme binding pocket with increased hydrophilic character. (C) 1998 Elsevier Science Inc. All rights reserved.