We have identified a 60 KDa thiol-protease which is associated with chromatin in zygotes of sea urchins. This enzyme was found to be present as a proenzyme in unfertilized eggs and activated shortly after fertilization. At pH values Of 7.8-8.0 which are normally found following fertilization, the enzyme degrades all five sperm-specific histones while the native cleavage stage (CS) histone variants remain unaffected. Based on the requirement for thiol groups, the inhibition by sulphydril blocking agents and the sensitivity to the cysteine-type protease inhibitors E-64, eistatin, and leupeptin this enzyme was defined as a thiol protease. Consistently, this protease was not affected by the serine-type protease inhibitors phenyl-methyl-sulfonyl- fluoride (PMSF) and pepstatin. The substrate selectivity and pH modulation shown by this enzyme strongly indicates a potential role in the removal of sperm- specific histones that occurs during the male pronucleus formation process. This suggestion was further supported by the inhibition of the sperm histone degradation induced in vivo by E-64.
|Publication status||Published - 1997|
ASJC Scopus subject areas
- Agricultural and Biological Sciences (miscellaneous)
- Biochemistry, Genetics and Molecular Biology(all)
- Cell Biology