Effect of <i>myo</i>-inositol(1,4,5)trisphosphate on the hydrolysis of phytic acid by phytase

Abstract

Phytase is a monomeric enzyme of molecular mass 160 kDa which catalyzes the hydrolysis of phytic acid (D<i>-myo </i>inositol hexakisphosphate, InsP₆) in a stepwise manner to <i>myo-</i>inositol.<i> </i>The enzyme-InsP_n (n = 1- 6) interaction at the<i> </i>catalytic site has a dissociation constant in the micro molar range. There also exists in the enzyme, a non-catalytic site<i> </i>specific for insP₃ with dissociation constant in the nano molar range. We have probed the effect of the high affinity InsP₃<i> </i>binding on the dissociation constant (<i>K</i>_d)<i> </i>of the phytase-InsP₆ interaction and the kinetics of hydrolysis. These studies<i> </i>demonstrate the effect exerted by the high affinity InsP₃ binding on the catalytic site of the enzyme.