Genes and Proteins Involved in Vanadium Accumulation by Ascidians

摘要

About a hundred years ago, Henze discovered high levels of vanadium in the blood (coelomic) cells of an ascidian collected from the Bay of Naples. The intracellular vanadium concentration of some species in the family Ascidiidae can be as high as 350 mM, which is 107 times the concentration in seawater Vanadium ions, thought to be present in the +5 oxidation state in seawater, are reduced to the +3 oxidation state via the +4 oxidation state and are stored in the vacuole of vanadocytes, the vanadium-containing cells, where high levels of protons and sulfate are also contained To investigate this unusual phenomenon, we have isolated many proteins and genes that might be involved in the accumulation and reduction of vanadium. To date, more than five types of vanadium-binding protein, designated as Vanabin family, have been isolated from vanadocytes In addition, four types of enzyme related to the pentose phosphate pathway that produces NADPH were revealed to be located in vanadocytes, and NADPH produced by the pentose phosphate pathway participates in the reduction of vanadium(V) to vanadium(IV).