Ascidia ceratodes

The ascidians or tunicates (sea squirts) accumulate vanadium from seawater (about 5x 10-8 mol dm-3) to a level of about 1 mol dm-3 and store it in a dilute solution of sulfuric acid (pH<2) in blood cells called vanadocytes. The tunicates thus concentrate vanadium several million-fold. 079 NMR, ESR and EXAFS determinations on whole vanadocyte cells of Ascidia ceratodes and Ascidia nigra indicate that the vanadium is present mainly as aquated V111 probably complexed with sulfate. Some vanadyl ion (5-10%) is also present.1080 1081... 

The presence of vanadium(III) complexes in the very acidic medium of the vacuoles of the signet ring cells in Ascidia ceratodes, containing one or two sulfato/hydrogensulfato ligands, has focused interest on sulfatovanadium complexes as model systems. " ] Whereas readily forms a 1 1 complex with sulfate K = 300 m ), the affinity of V to sulfate is less pronounced. Selected stability constants and pA a values obtained from... 

Francis JT, Enkvist C, Lunell S, Hitchcock AP (1994) Studies of X Is to n triplet states of carbon monoxide, benzene, ethylene, and acetylene. Can J Phys 72 879-884 Frank P, Hedman B, Carlson RMK, Hodgson (1994) Interaction of vanadium and sulfate in blood cells from the tunicate Ascidia ceratodes Observations using X-ray absorption edge structure and EPR spectroscopies. Inorg Chem 33 3794-3803... 

Frank P, Hedman B, Hodgson (1999) Sulfur allocation and vanadium-sulfate interactions in whole blood cells from the tunicate Ascidia ceratodes, investigated using X-ray absorption spectroscopy. Inorg Chem 38 260-270... 

Vertebrates probably arose from urochordate-like ancestors, and the point would be bolstered if eicosanoids also acted in reproduction within modern urochordates. Perry and Lambert [11] showed that eggs of the tunicate Ascidia ceratodes are competent to metabolize arachidonic acid into more polar products. 

This biosynthetic hypothesis is currently supported by the discovery of peptides and proteins containing DOPA and TOPA in blood cells of several species of ascidian. The first of these is hemovanadin, highlighted in 1948 in the cell lysate (Henze solution) of Phallusia mamillata (Colifano and Caselli, 1949). This protein is composed of two subunits, each of 27 kDa, but its structure does not appear to have been elucidated (Bielig and Bayer, 1954). Polypeptides rich in DOPA and TOPA were isolated and partly characterized in Ascidia ceratodes (Abcp-A, -B, -C, and -D) and Molgula manhattensis (Mbcp-A and Mbcp-B). ... 

Table 28.14 Main complexes of vanadium in Ascidia ceratodes and Phallusia nigra...

Frank, P., Carlson, R.M.K., and Hodgson, K.O. (1986) Vanadyl ion EPR as a non-invasive probe of pH in intact vanadocytes from Ascidia ceratodes. Inorg. Chem., 25, 470-478. 

Kustin, K., Robinson, W.E., Erankel, R.B., and Spartalian, K. (1996) Magnetic properties of tunicate blood cells. II. Ascidia ceratodes. J. Inotg. Biochem., 63, 223-229. 

Robinson, W.E., Kustin, K., Matulef, K., Parry, D.L, He, X., and Ryan, E.K. (1996) C- and H-tyrosine incorporation into Ascidia ceratodes tunichrome in vivo. Comp. Biochem. Physiol., 115B, 475—481. 

Taylor, S.W., Ross, M.M., and Waite, J.H. (1995) Novel 3,4-di- and 3,4,5-trihydroxyphenyIalanine-containing polypeptides from the blood cells of the ascidians Ascidia ceratodes and Mdgula manhattensis. Arch. Biochem. Biophys., 324, 228-240. 

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