Fertilization results in the tyrosine phosphorylation of several egg protei
ns and studies have shown that tyrosine protein kinase activity is required
for successful fertilization. The Fyn protein kinase has been detected in
eggs of the sea urchin, frog and rat, although measurement of fertilization
induced changes in Fyn kinase activity have only been successful in the se
a urchin system. The present study demonstrates the presence of Fyn kinase
in the zebrafish egg and the stimulation of this enzyme at fertilization. A
ctivation of Fyn was detected as early as 30 seconds post-fertilization and
increased approximately six-fold by 2 minutes post-insemination. The activ
ation of Fyn in the zebrafish egg required sperm and was not observed in sp
ontaneously activated eggs.