Biochemical characteristics of yolk proteins in Japanese eel: Involvement of selective yolk proteolysis in modulation of egg buoyancy
2006
Matsubara, T.(Hokkaido National Fisheries Research Inst., Kushiro (Japan)) | Andoh, T. | Ohkubo, N. | Sawaguchi, S.
Maturation-associated hydration via controlled proteolysis of yolk proteins is the main event in cytoplasmic maturation of oocytes in marine pelagic egg spawning teleost. Failure of such the event likely reflects low fertilizability of eggs and high mortality of embryos. To improve "egg quality" of Japanese eel, we tried to elucidate biochemical characteristics of yolk proteins and their molecular alterations during oocyte maturation. Three forms of vitellogenin (Vg) appear to exist in Japanese eel, including two types of complete Vg (Vg 1 and Vg 2 ) and phosvitinless Vg (PvlVg). Thee classes of yolk protein which are derived from the Vgs play distinct roles in regulation of oocyte hydration through selective proteolysis in oocytes undergoing oocyte maturation. The regulation system of oocyte hydration in Japanese eel is unique and completely different from those in teleost members of higher taxa, eg. Acanthopterigii. We discussed here the characteristics of yolk proteins and their possible roles in regulation of egg buoyancy, with respect to improvement of egg quality in the Japanese eel.
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