Marine taurine

James MO, JR Bend (1976) Taurine conjugation of 2,4-dichlorophenoxyacetic acid and phenylacetic acid in two marine species. Xenobiotica 6 393-398. 

It is an ideal compound for regulation of osmotic pressure, since it has a low molecular mass, is highly soluble and has no net charge. It serves this function in some of the tissues of elasmobranch fish such as the skate and shark, and in marine invertebrates. Any damage to these tissues releases taurine, which is used as a chemoattractant for predators such as the shrimp, which wiU attack small fish. 

A quantitatively important pathway of cysteine catabolism in animals is oxidation to cysteine sulfinate (Fig. 24-25, reaction z),450 a two-step hydroxyl-ation requiring 02, NADPH or NADH, and Fe2+. Cysteine sulfinic acid can be further oxidized to cyste-ic acid (cysteine sulfonate),454 which can be decarbox-ylated to taurine. The latter is a component of bile salts (Fig. 22-16) and is one of the most abundant free amino acids in human tissues 455-457 Its concentration is high in excitable tissues, and it may be a neurotransmitter (Chapter 30). Taurine may have a special function in retinal photoreceptor cells. It is an essential dietary amino acid for cats, who may die of heart failure in its absence,458 and under some conditions for humans.459 In many marine invertebrates, teleosts, and amphibians taurine serves as a regulator of osmotic pressure, its concentration decreasing in fresh water and increasing in salt water. A similar role has been suggested for taurine in mammalian hearts. A chronically low concentration of Na+ leads to increased taurine.460 Taurine can be reduced to isethionic acid... 

Marine Sulfur metabolites bearing a Taurine Residue... 

In addition to quaternary pyridine compounds homarine, 101, and trigonelline, 102, (Section 2.3.4), Cellaria spp. and Chartella papyra-cea also contained betaine, 115, taurine, 116, and tetramethylammo-nium ion, 117. Betaine, 115, was also found in Bugula neritina. These compounds occur in other marine invertebrates as well 144). 

In several fish species and one marine crustacean, taurine conjugates of xenobiotic carboxylic acids have been Isolated from urine (fish) or hepatopancreas (Crustacea) and subjected to unequivocal chemical characterization (77-82). Table VIZ shows which acids are conjugated with taurine in some marine species. 

Urinary Catheter. An appreciable amount of drug as parent or metabolites may be excreted in the urine of fish. A number of studies have demonstrated that glucuronide, sulfate and taurine conjugates are excreted by the fish kidney as a result of anion/cation carrier-mediated mechanisms (44,45). Urine has been collected for xenobiotic studies in a variety of fish species including flounder (46), dogfish shark (47), rainbow trout (Kleinow, K.M. Can. J. Fish Aq. Sci., in press) and catfish (48). In large measure urine production is greater in freshwater fish as compared to marine species. 

A new ninhydrin-reactive substance, AT-(l-carboxyethyl)taurine (196) has been isolated from three species of marine red algae. It had the same m.p. and Rf values as the crystals obtained by reacting a-bromopropionic acid with taurine141. 

The metabolism of 35S-labelled sulphur amino acids in marine and fresh water invertebrates has been studied and reviewed by Awapara and coworkers179 180. The general conclusion drawn from these studies was that the metabolism of sulphur-bearing amino acids in two molluscs studied is qualitatively the same as in mammals. Taurine, which serves as an osmoregulator in marine molluscs, is formed either by decarboxylation of cysteic acid (in Rangia cuneata) or by oxidation of hypotaurine (in Mytilus edulis), derived from cysteinesulphinic acid by decarboxylation. In Arenicola cristata only the terminal reactions are different. Methionine and cysteine sulphur incorporates into taurocyamine by transamidation between taurine and arginine. 

The more complex sulphur requirements of the marine animals are met largely by cysteine, cystine, methionine, biotin, and thiamine (Young and Maw, 1958) (Fig. 4). Cysteine is a component of the tripeptide glutathione and a precursor of taurine. Methionine is as an essential amino acid involved in biosynthesis of proteins, creatine and adrenaline. Adenosylmethionine is considered to be the active part in transmethylation, e.g. of choline. Methionine is part of the pathways to homocysteine, cystathionine and methylthioadenosine (Young and Maw, 1958). Various organisms convert cysteine and/or cystine into mercapturic acids, cysteine sulphinic acid, and thiazolidine derivatives (Zobell, 1963). 

In invertebrates, taurine appears to participate in osmoregulation, in particular in marine animals . In mammals, the high concentration of taurine in lens has been thought to have an osmoregulatory function ... 

C. D. Kochakian, Taurine and related sulfur compounds in the reproductive tract of marine animals, in "Taurine" R. Huxtable and A. Barbeau (Eds), p 575 Raven Press,... 

Zhang, H. and Capon, R.J. (2008) Phorbasins D-F diterpenyl-taurines from a Southern Australian marine sponge, Phorbas sp. Org. Lett., 10, 1959-1962. 

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