PRESSURE EFFECTS ON THE HYPERVALENT MEAT PIGMENT FERRYLMYOGLOBIN

Acid-catalyzed autoreduction of ferrylmyoglobin [MbFe(TV)=O] decreased with increasing hydrostatic pressure corresponding to a volume of act ivation of Delta V '' =+7.2+/-0.8 mi mol(-1), as determined for pressu res of up to 250 MPa at 15 degrees C in acidic 0.16 M NaCl solution. F or the non-catalyzed autoreduction, a significant increase in compress ibility for the non-photonated heme pigment, corresponding to a compre ssibility coefficient of activation of Delta kappa(#) = +(4.0+/-1.1)x1 0(-8) mi mol(-1) Pa-1, moderates the effects of pressure, although the volume of activation determined at 30 degrees C was comparable, i.e. Delta V-# = +7.5 +/- 2.0 mol mol(-1). At pH relevant for meat, the eff ect of pressure on the transformation of ferrylmyoglobin to metmyoglob in [MbFe(III)] was approximately half that of the same pressure on the transformation of oxymyoglobin to metmyoglobin, when compared on a lo garithmic basis. This result finds a surprising parallel in the temper ature-dependence of the same acid-catalyzed processes to yield metmyog lobin.