Purification and characterization of zebrafish hatching enzyme – an evolutionary aspect of the mechanism of egg envelope digestion

There are two hatching enzyme homologues in the zebrafish genome: zebrafish hatching enzyme ZHE1 and ZHE2. Northern blot and RT‐PCR analysis revealed that ZHE1 was mainly expressed in pre‐hatching embryos, whereas ZHE2 was rarely expressed. This was consistent with the results obtained in an experim...

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Bibliographic Details
Published in:	European journal of biochemistry 2008-12, Vol.275 (23), p.5934-5946
Main Authors:	Sano, Kaori, Inohaya, Keiji, Kawaguchi, Mari, Yoshizaki, Norio, Iuchi, Ichiro, Yasumasu, Shigeki
Format:	Article
Language:	eng
Subjects:	Amino Acid Sequence Animals astacin family Biochemistry Catalysis Chromatography, High Pressure Liquid Danio rerio egg envelope Egg Proteins - chemistry Egg Proteins - genetics Egg Proteins - metabolism Electrophoresis, Polyacrylamide Gel Embryo, Nonmammalian - enzymology Embryo, Nonmammalian - metabolism Enzymes Evolution, Molecular Evolutionary biology Freshwater Gene Expression Regulation, Developmental Gene Expression Regulation, Enzymologic Genomics hatching enzyme In Situ Hybridization Kinetics Membrane Glycoproteins - chemistry Membrane Glycoproteins - genetics Membrane Glycoproteins - metabolism Metalloendopeptidases - chemistry Metalloendopeptidases - genetics Metalloendopeptidases - metabolism molecular evolution Molecular Sequence Data Molecular Weight Oryzias - genetics Oryzias - metabolism Oryzias latipes Receptors, Cell Surface - chemistry Receptors, Cell Surface - genetics Receptors, Cell Surface - metabolism Recombinant Proteins - biosynthesis Recombinant Proteins - chemistry Species Specificity Substrate Specificity Teleostei Zebrafish Zebrafish - genetics Zebrafish - metabolism Zona Pellucida - enzymology Zona Pellucida - metabolism Zona Pellucida Glycoproteins Zygote - enzymology Zygote - metabolism
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Summary:	There are two hatching enzyme homologues in the zebrafish genome: zebrafish hatching enzyme ZHE1 and ZHE2. Northern blot and RT‐PCR analysis revealed that ZHE1 was mainly expressed in pre‐hatching embryos, whereas ZHE2 was 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. Therefore, the hatching of zebrafish embryo is performed by a single enzyme, different from the finding that the medaka hatching enzyme is an enzyme system composed of two enzymes, medaka high choriolytic enzyme (MHCE) and medaka low choriolytic enzyme (MLCE), which cooperatively digest the egg envelope. The six ZHE1‐cleaving sites were located in the N‐terminal regions of egg envelope subunit proteins, ZP2 and ZP3, but not in the internal regions, such as the ZP domains. The digestion manner of ZHE1 appears to be highly analogous to that of MHCE, which partially digests the egg envelope and swells the envelope. The cross‐species digestion using enzymes and substrates of zebrafish and medaka revealed that both ZHE1 and MHCE cleaved the same sites of the egg envelope proteins of two species, suggesting that the substrate specificity of ZHE1 is quite similar to that of MHCE. However, MLCE did not show such similarity. Because HCE and LCE are the result of gene duplication in the evolutionary pathway of Teleostei, the present study suggests that ZHE1 and MHCE maintain the character of an ancestral hatching enzyme, and that MLCE acquires a new function, such as promoting the complete digestion of the egg envelope swollen by MHCE.
ISSN:	1742-464X 0014-2956 1742-4658 1432-1033