Change in the Fructose 1, 6-Bisphosphatase Activity in Sea Urchin Eggs Following Fertilization

Abstract

The activity of fructose 1, 6-bisphosphatase [EC 3.1.3.11] in sea urchin eggs decreased following fertilization. During the first 30min after fertilization, the activity was considerably lower than that in unfertilized eggs, but by 30min the activity was similar to that in unfertilized eggs. The enzyme activity in fertilized eggs, estimated in the presence of EGTA, was similar to that in unfertilized eggs. The activity in unfertilized eggs was reduced by Ca²⁺ at concentrations between 1×10^-5M and 5×10^-3M. Immediately after fertilization, the enzyme was insensitive to concentrations of Ca²⁺ lower than 2×10^-4M, but the Ca²⁺ sensitivity of the enzyme recovered 30min after fertilization. In the presence of Ca²⁺ at concentrations higher than 2×10^-4M, the enzyme activity in unfertilized eggs was similar to that in fertilized eggs. Mg²⁺ restored the Ca²⁺-induced inhibition of fructose 1, 6-bisphosphatase. 3-Phos-phoglycerate and citrate hardly affected the enzyme activity, and AMP at concentrations above 10mM inhibited it.