EFFECT OF HEPARIN AND DEXTRAN SULFATE ON THE ACTIVITY OF GLUTATHIONE-REDUCTASE FROM YEAST

Glutathione reductase (EC 1.6.4.2) is a pivotal enzyme of the glutahio ne antioxidant system in a cell. The kinetic studies of the interactio n of glutathione reductase with unfractionated and low molecular weigh t heparin and dextran sulfate can contribute to explanation of polyani ons effect on the conformation changes of glutathione reductase. The t ested polyanions inhibit this enzyme and the inhibition effect depends on the ionic strengths and pH value. The most potent inhibitor is dex tran sulfate (ID50 is 4.1 mu g/ml, pH=6.8, without NaCl). The ionic st rength ( > 100 mM) allows the reactivating of GR if the concentration of DS is not higher than 80 mu g/ml. The inhibition effect of tested p olyanions is caused by electrostatic interactions with enzyme; the kin etic analyses indicate that it is a mixed inhibition with respect to o xidized glutathione or NADPH.