PH EFFECT ON THE FUNCTIONAL-PROPERTIES OF LACTATE-DEHYDROGENASE DURING OF OOCYTES MATURATION OF FISHES

The change of kinetical properties and pH optima of LDN has been obser ved to occur during maturation of loach oocytes. The K(m) values for p yruvate reach respective minima at 5-degrees-C and 10-12-degrees-C in immature oocytes and mature unfertilized eggs respectively. pH optima are 8,0 for the enzyme from immature oocytes and 7,7 for that from mat ure eggs. The change of kinetical properties and pH optima during matu ration of oocytes is linked to decrease in intracellular pH. This valu e equals 7,45 in immature oocytes and 6,66 in mature eggs. The pH effe ct on LDH activity during maturation of oocytes can be linked to proto nation-deprotonation of histidine in the active site of the enzyme.