Effects of Vanadium Ions in Different Oxidation States on Myosin ATPase Extracted from the Solitary Ascidian, Halocynthia roretzi (Drasche) : Biochemistry

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Some ascidians are known to accumulate vanadium ion within their tissues by 10^6-fold as that in sea water and store the metal ion in its reduced tetravalent and/or trivalent states. It is also well known that phosphoenzymes are inhibited by pentavalent vanadium ion over a range of 10nM to 1mM. In the present experiment we have therefore examined the effects of vanadium ions in different oxidation states on the activity of myosin ATPase extracted from the mantle of the ascidian, Halocynthia roretzi, in order to know the mechanism for protectin phosphoenzymes against inhibition by the massive amounts of vanadium ion within their tissues. The activity of myosin ATPase was inhibited by pentavalent vanadium ion but was not inhibited by tetravalent or trivalent vanadium ion. The addition of 5mM ascorbic acid, which is known to reduce pentavalent vanadium ion to tetravalent state, to the reaction mixture reduced the inhibitory effect of pentavalent vanadium ion on the ATPase. Based on the results, one of the reasons that the ATPase within the ascidian is not inhibited in vivo, in spite of the high level of vanadium within ascidian tissues, may be that the pentavalent vanadium ion which is accumulated from sea water is readily reduced to the tetravalent and/or trivalent oxidation states by the endogenous reducing substances in ascidian tissues.
社団法人日本動物学会の論文
1989-04-15