Vanadium in tunicates: Oxygen-binding studies

Macara, Ian G.; McLeod, G. C.; Kustin, Kenneth

doi:10.1016/0300-9629(79)90009-4

Cited by 47 publications

(25 citation statements)

References 12 publications

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“…Blood was removed and extracted with 0.1 M-HCl as previously described (Macara et al, 1979). To raise the pH above 2, 0.5M-sodium citrate, pH2.4, was added, and the extract was loaded on to a column (2.5 cmx 1Ocm) of Sephadex LH-20.…”

Section: Purification Of Tunichromementioning

confidence: 99%

“…It is stored in acidic vacuoles, as either V(IV) (the Aplousobranchia) or as a mixture of V(IV) and V(III) (the Phlebobranchia) (Rezaeva, 1964;Swinehart et al, 1974). This type of vacuole, and hence the blood as a whole, often appears green-yellow, a colour produced not by the vanadium as was once believed (Bielig et al, 1966; Goodbody, 1974), but by an organic chromogen (Swinehart et al, 1974;Gilbert etal., 1977;Macara et al, 1979) for which we propose the trivial name tunichrome. Tunichrome is readily oxidized by molecular 02, Fe(III) and V(V) (Swinehart et al, 1974;Macara et al, 1979).…”

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confidence: 99%

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Isolation, properties and structural studies on a compound from tunicate blood cells that may be involved in vanadium accumulation

Macara¹,

McLeod²,

Kustin³

1979

Biochemical Journal

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A novel compound, for which the trivial name tunichrome is proposed, was isolated from the vanadium-rich blood cells of the tunicate Ascidia niga. Preliminary structural studies suggest a molecular weight of about 390, the presence of conjugated vinyl groups, and an acidic group, possibly carboxyl, with an apparent pKa of 3.0. Elements C, H, N and O comprise 98.4% of the sample weight, the number of atoms per mol of tunichrome being 14.1, 22.2, 1.5 and 10.6 respectively, which indicates some heterogeneity in the sample. Tunichrome readily reduces Fe(III) and V(V). In an initial fast step, 2 mol of V(V) are reduced, or 4 mol of Fe(III)-phenanthroline per mol of tunichrome; in a further slow reaction, another 9 mol of Fe(III)-phenanthroline or Fe(III)-bipyridine are reduced. The initial reaction is first-order with respect to tunichrome and Fe(III). Above pH 3.5, tunichrome is rapidly hydrolysed, 13 mol of OH- being consumed per mol of tunichrome. The hydrolysis involves polymerization and loss of the characteristic absorption peak at 325 nm. It is suggested that the presence of tunichrome may be linked to vanadium accumulation by the blood cells. The mechanism involves entry of vanadate via an anionic channel into vacuoles of the blood cells, where it is reduced to V(IV) or V(III), both of which, being cationic, cannot escape from the vacuole.

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Section: Purification Of Tunichromementioning

confidence: 99%

mentioning

confidence: 99%

Isolation, properties and structural studies on a compound from tunicate blood cells that may be involved in vanadium accumulation

Macara¹,

McLeod²,

Kustin³

1979

Biochemical Journal

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“…We consider possibility 2 to be less likely because much of the endogenous vanadium(III) is liberated as the free metal ion on blood cell lysis (27). DISCUSSION Kustin et al (38) were first to question the then predominant view that there was a single "vanadocyte" in ascidian blood.…”

Section: Figmentioning

confidence: 99%

“…This solitary ascidian ranges along the warm waters of the southern Atlantic coast of North America and the Caribbean (25)(26)(27). The blood cells of A. nigra are known to be rich in vanadium, principally as V(III) (14,27). From SQUID 2 magnetometry studies, it was shown that A. nigra blood cell vanadium also includes a moderate percentage (Յ20%) of vanadyl ion (14), in contrast to A. ceratodes (9 -13, 28).…”

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Vanadium K-edge X-ray Absorption Spectroscopy Reveals Species Differences within the Same Ascidian Genera

Frank¹,

Kustin²,

Robinson³

1998

Journal of Biological Chemistry

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Vanadium K-edge x-ray absorption spectroscopy (XAS) was used to examine whole blood preparations from the tunicates Ascidia nigra and Ascidia ceratodes. Each XAS spectrum exhibits a rising edge inflection near 5480 eV characteristic of vanadium(III) and an intensity maximum at 5484.0 eV. In A. ceratodes blood cells, intrinsic aquo-VSO 4 ϩ complex ion is indicated by an inflection feature at 5476 eV in the first derivative of the vanadium K-edge XAS spectrum, but this feature is notably absent from the first derivative of the vanadium K-edge spectrum of blood cells from A. nigra. A strong pre-edge feature at 5468.6 eV also uniquely distinguishes the vanadium K-edge XAS spectrum of A. nigra blood cells, implying that vanadyl ion represents ϳ25% of the endogenous vanadium. However, the energy position of the rising edge inflection of the vanadium K-edge XAS spectrum of A. nigra (5479.5 eV) is 1 eV lower than that of A. ceratodes (5480.5 eV), the reverse of any expected shift arising from the endogenous vanadyl ion. Thus, in contrast to A. ceratodes, a significant fraction of the blood cell vanadium(III) in A. nigra is apparently in a ligation environment substantially different from that provided by water. These novel species-related differences may have taxonomic significance.The bioinorganic chemistry of vanadium in ascidians has been of increasing interest in the past several years, resulting in a steady clarification of problems regarding the distribution and intracellular status of this metal ion (1-4). In solitary phlebobranch ascidians, vanadium is concentrated within blood cells up to several million times the ambient seawater concentration. In addition, blood cell vanadium is typically reduced from oceanic V(V)-vanadate to V(IV) or V(III) (5-20). There is no evidence for

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Vanadocytes, cells hold the key to resolving the highly selective accumulation and reduction of vanadium in ascidians

Michibata

Uyama

Ueki

et al. 2002

Microscopy Res & Technique

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Since Henze discovered vanadium in the blood (or coelomic) cells of an ascidian in 1911, this unusual phenomenon has attracted the interest of many investigators. The highest concentration of vanadium (350 mM) in the blood cells of Ascidia gemmata, which belongs to the suborder Phlebobranchia, is 10(7) times higher than that in seawater. Of the approximately 10 types of blood cells, a combination of cell fractionation and neutron-activation analysis revealed that the signet ring cells were the true vanadocytes. In the vanadocytes, 97.6% of the vanadium is in the +3 oxidation state (III). The extremely low pH of 1.9 found in vanadocytes suggests that protons, concentrated by an H(+)-ATPase, might be linked to the accumulation of vanadium energetically. The antigen recognized by a monoclonal antibody, S4D5, prepared to identify vanadocytes, was determined to be 6-PGDH in the pentose phosphate pathway. NADPH produced in the pentose phosphate pathway in vanadocytes is thought to participate in the reduction of vanadium(V) to vanadium(IV). During embryogenesis, a vanadocyte-specific antigen first appears in the body wall at the same time that significant accumulations of vanadium become apparent. Three different vanadium-associated proteins (VAPs) were extracted from the blood cells of vanadium-rich ascidians. These are 12.5, 15, and 16 kDa in size and are associated with vanadium in an approximate ratio of 1:16. The cDNA encoding the 12.5 and 15 kDa VAPs was isolated and the proteins encoded were found to be novel. Further biochemical and biophysical characterization of the VAPs is in progress.

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Vanadium in tunicates: Oxygen-binding studies

Cited by 47 publications

References 12 publications

Isolation, properties and structural studies on a compound from tunicate blood cells that may be involved in vanadium accumulation

Isolation, properties and structural studies on a compound from tunicate blood cells that may be involved in vanadium accumulation

Vanadium K-edge X-ray Absorption Spectroscopy Reveals Species Differences within the Same Ascidian Genera

Vanadocytes, cells hold the key to resolving the highly selective accumulation and reduction of vanadium in ascidians

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