Physiochemical Study on Highly Selective Accumulation of Vanadium Ions by Ascidians

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A lot is known about the vanadium in ascidians, which are also known as tunicates or sea squirts. For example, the concentration of vanadium attains 350 mMin the blood cells of Ascidia gemmata belonging to the suborder Phlebobranchia, which is l0^7times higher than the concentration in sea water among approximately ten types of blood. cells, signet ring cells are true vanadocytes, vanadium-containing blood cells, almost all vanadium is reduced to the +3 oxidation state (V^<III>) via the +4 oxidation state (V^<IV>) and stored in vacuoles of vanadocytes, although vanadium is in the +5 oxidation state (V^V) in seawater.We have revealed by the research project followings : a vanadium-associated protein (VAP) extracted from the blood cells of A.sydneiensis sames was revealed to contain 16 atoms of vanadium per a mol ; the same antigen recognized with a polyclonal antibody against VAP was detected in the precipitated proteins of the polychaete Pseudopotamilla occelata which was the first animal revealed to contain high levels of vanadium besides ascidians ; apo-VAP, VAP removed vanadium, was found to bind 10 atoms of vanadium ; the nucleotide sequences of cDNAs encoding 12.5 kDa and 15 kDa of VAPs are revealed ; a fusion protein was isolated from E.coil transfected with plasmid vector expressing VAPs genes ; a monoclonal antibody specific to vacuolar membrane of vanadocytes was prepared ; G6PDH, 6PGDH, and transketolase in the pentose phosphate pathway and glycogen phosphorylase were found to be in the cytoplasm of vanadocytes ; NADPH was revealed to reduce V^V-EDTA to V^<IV>-EDTA.