Arsoniumphospholipid in algae

Abstract

A novel phospholipid containing arsenic was formed by all marine algae culture in [74Aslarsenate. Compo-nents of the labeled algal extracts readily separated by twodimensional paper radiochromatography. Base-catalyzed deacylation of the major lipid yielded a phosphodiester identical to one of the two major water-soluble compounds. Acid or enzymic hydrolysis of the phosphodiester produced a product identified as trimethylarsoniumlactic acid. The structure of the phospholipid therefore is O-phosphatidyltrimethylarsoniumlactic acid. Detoxication of arsenate by marine algae leads to accumulation of the arsoniumphospholipid as a major reservoir for arsenic. Its degradation to trimethylarsoniumbetaine, dimethylarsinic acid, methanearsonic acid, and arsenate in marine food chains and its metabolism in human beings are of considerable interest. Oceanic phosphate levels, reduced at the surface by phytoplankton and bacterial consumption, approach those of arsenate. In tropical waters, and especially the Sargasso Sea, arsenate concentrations even exceed those of phosphate (1, 2). Both ions are absorbed by their common transport system. Marine algae have developed effective procedures for detoxicating arsenate which, if it were allowed to accumulate to 1 ;4M, could cause serious uncoupling of phosphorylation. Bacteria (3), corals (4), and algae (5) reduce arsenate to arsenite which, similarly, would inhibit sulfhydryl enzymes of glycolysis at 1 mM unless it were further metabolized. Recognition of very low concentrations of methanearsonic acid and of dimethylarsinic acid (cacodylic acid) and their measurement by Andreae (6) Chromatography. Concentrated cell extracts were chromatographed two dimensionally on Whatman no. 4 paper and radioautograms were prepared (9). The orange dye, Tropaeolin 000, was an invaluable chromatographic reference.Paper Electrophoresis. Eluted or cutout (2 X 2 mm) samples of radioactive components from paper chromatograms were separated by paper electrophoresis (10 V/cm) in a variety of buffer systems. The blue dye, indigotetrasulfonate, was used as a standard and applied as 2 X 2 mm samples onto the wet paper adjacent to each origin. RESULTSThin-layer chromatography of the CHCIa/MeOH extract of the marine diatom C. concavicornis revealed three main 74As-containing spots, lipid compounds I, II, and III (Table I). Four water-soluble compounds (A, B, C, and D) were resolved by two-dimensional paper chromatography of the water extract (Table 2 and Fig. 1).Both lipids I and II deacylated upon treatment with methanolic KOH. Chromatography revealed the identity of the deacylated compound and the naturally occurring compound B. Treatment of lipid I with phospholipase A2 produced a compound with the same RF as lipid II, implying that lipid II is the lyso form of lipid I.The deacylated lipid (B) was found to acetylate in acetic anhydride/pyridine. Both mono-and diacetylated products were bbserved by paper chromatography. Oxidation of B with NaIO4 resulted in a new compound with RF = 0.48. A compou...

Cyanobacteria produce arsenosugars

“…[26] Thus, the genus Nostoc generally may not have the ability to produce Oxo-PO 4 . Because Oxo-PO 4 has been shown to be degraded to Oxo-Gly by an in vitro enzyme (glycerophosphorylcholine diesterase) reaction, [40,41] Oxo-PO 4 might be biosynthesised from Oxo-Gly by some oppositely oriented reaction in cyanobacteria, and Nostoc may not have the responsible enzyme(s). Alternatively, As V concentrations ($0.1 mM) in the medium in this study might have been too high for Nostoc sp.…”

Arsenosugar phospholipids and arsenic hydrocarbons in two species of brown macroalgae

“…[1] Although most of the arsenic compounds identified so far have been water-soluble species, the early work on arsenic marine chemistry focussed on lipidsoluble compounds, so called arsenolipids. [2][3][4] Identification of these arsenolipids proved difficult, however, and it was not until 1988 that an arsenolipid was first rigorously characterised and identified as an arsenosugar-containing phospholipid [5] (see Table 1, compound As-PL958).Subsequently, the range of naturally occurring arsenolipids has been extended with the discovery of arsenic-containing fatty acids in fish oils, [6] and arsenic-containing hydrocarbons in fish oils, [7] fish liver, [8] sashimi tuna [9] and fish meal. [10] The origin of these compounds was presumed to be algae.…”

“…[1] Although most of the arsenic compounds identified so far have been water-soluble species, the early work on arsenic marine chemistry focussed on lipidsoluble compounds, so called arsenolipids. [2][3][4] Identification of these arsenolipids proved difficult, however, and it was not until 1988 that an arsenolipid was first rigorously characterised and identified as an arsenosugar-containing phospholipid [5] (see Table 1, compound As-PL958).…”

“…The early experiments of Benson and co-workers provide some information on the biochemical processes involved. [3] By using radiolabelled arsenic and monitoring products by radiochromatography, they showed that unicellular algae take up arsenate from seawater and convert it into lipid-and watersoluble arsenic species. By selective use of enzymes (e.g.…”

Arsenic‐Containing Phosphatidylcholines: A New Group of Arsenolipids Discovered in Herring Caviar

“…Arsenic‐containing lipids, so‐called arsenolipids, are natural constituents of marine organisms thought to be involved in arsenic detoxification processes 1, 2. The first arsenolipid to be rigorously identified was an arsenosugar lipid which was isolated from a brown alga 3.…”