N‐acetyl‐β‐D‐glucosaminidase activity in the cortical granules of Xenopus laevis eggs

Abstract

AbstractThe glycosidase activities associated with Xenopus laevis eggs were determined using p‐nitrophenyl glycosides as substrates. The egg lysate contained significant amounts of α‐fucosidase, N‐acetyl‐β‐D‐galactosaminidase, and α‐mannosidase activities with smaller amounts of other glycosidase activities, including N‐acetyl‐β‐D‐glucosaminidase. A cortical granule exudate obtained from ionophore‐activated dejellied eggs contained predominantly glucosaminidase activity with only trace amounts of other glycosidase activities. Perivitelline space material obtained from activated or fertilized jellied eggs contained only glucosaminidase activity. Using cytochemical staining procedures, glucosaminidase activity was present in the perivitelline space and the inner aspect of the jelly coat after fertilization or activation of the egg, but not before. The rate of glucosaminidase activity released from activated eggs occurred with the same kinetics as the cortical reaction. The cortical granule and noncortical granule glucosaminidase activities had different electrophoretic mobilities as determined by disc gel electrophoresis. Thus, the Xenopus laevis egg has two N‐acetyl‐β‐D‐glucosaminidase activities, one associated with the cortical granules and the other associated with the noncortical granule compartment of the cell. The cortical granule enzyme released from the egg at fertilization may function in altering the egg's penetrability to supernumerary sperm.