We purified eel hatching enzyme (EHE) from the hatching liquid of Japa-nese eelAnguilla japonicabelonging to Elopomorpha to a single band on
SDS⁄PAGE. TOF-MS analysis revealed that the purified EHE contained
several isozymes with similar molecular masses.
We purified two hatching enzymes, namely high choriolytic enzyme (HCE;
EC 188.8.131.52) and low choriolytic enzyme (LCE; EC 184.108.40.206), from the
hatching liquid ofFundulus heteroclitus, which were named FundulusHCE
(FHCE) and FundulusLCE (FLCE). FHCE swelled the inner layer of egg
envelope, and FLCE completely digested the FHCE-swollen envelope.
The hatching enzyme of oviparous euteleostean fishes consists of two
metalloproteases: high choriolytic enzyme (HCE) and low choriolytic
enzyme (LCE). They cooperatively digest the egg envelope (chorion) at the
time of embryo hatching. In the present study, we investigated the hatching
of embryos of the ovoviviparous black rockfish Sebastes schlegelii.
Two cDNA homologues of medaka hatching enzyme)high choriolytic
enzyme (HCE) and low choriolytic enzyme (LCE) – were cloned from
Fundulus heteroclitusembryos. Amino acid sequences of the mature forms
ofFundulusHCE (FHCE) and LCE (FLCE) were 77.9% and 63.3% iden-tical to those of medaka HCE and LCE, respectively. In addition, phylo-genetic analysis clearly showed that FHCE and FLCE belonged to the
clades of HCE and LCE, respectively.
There are two hatching enzyme homologues in the zebrafish genome:
zebrafish hatching enzymeZHE1andZHE2. Northern blot and RT-PCR
analysis revealed that ZHE1 was mainly expressed in pre-hatching
embryos, whereasZHE2was rarely expressed. This was consistent with the
results obtained in an experiment conducted at the protein level, which
demonstrated that one kind of hatching enzyme, ZHE1, was able to be
purified from the hatching liquid.