Low intensity ultrasonic effects on yeast hexokinase

The kinetics of yeast hexokinase activity exposed to 1 MHz ultrasound of therapeutic intensities 0.1-1.5 W/cm2 was studied using traditional physico-chemical methods and by the thermoinactivation approach. Analysis of the kinetic curves and the kinetic parameters, obtained by two independent methods, suggested specific perturbation processes provoked by the ultrasonic waves, viz., the mechanical breakdown of the contact site between monomer units and the subsequent sonochemical modification of the active enzyme site. Low intensity ultrasound also caused the destabilization of the molecular structure of hexokinase as revealed by the apparent thermolability of the sonicated enzyme.