TIURINE IN MARINE INVERTEBRATES
227
present in Asterias but as yet undetected. The only proof that in
invertebrates taurine gives rise to taurocyamine has been given by
Abbott and Awapara (1960). Following the injection of high specific
activity S35 taurine into Areniwla they were able to detect after 12 h a
slight amount of radioactivity in the taurocyamine. In vitro, and in one
case, they showed transamidination between arginine and taurine with
the formation of a small amount of taurocyamine (p. 225) Transamidination betwecn arginine and hypotaurine, giving hypotaurocyamine
(2-guanidoethanesulphinic acid) with subsequent oxidation to taurocyamine has been shown to occur in Areniwla and Phaswlosoma
(Thoai et a,!., 1963). In Areniwla, transamidination occurs in the gut
and oxidation in muscle, whereas in Phaswlosoma oxidation occurs in
the gut but not in the muscle of the body wall. As a result, Areniwla
muscle contains ten times as much taurocyamine as hypotaurocyamine,
while the reverse is true of body wall muscle of Phscolosoma. The
inability of the muscle of the body wall of Phaswlosoma to oxidize
hypotaurocyamine is attributed to low external oxygen tension.
Details of the enzymes involved in this pathway are given by Thoai,
1957; Thoai et al., 1963a and b; Thoai and Robin, 1965; Thoai and
Pradel, 1962a and b ; Thoai and Roche, 1960; Kassab et al., 1965;
Hobson and Rees, 1957 ; and Ennor and Morrison, 1958. The metabolic fate of taurocyamine is unknown.
Little is known of the other two derivatives of taurine found in
invertebrates, except that taurobetaine was originally identified in the
sponge Geodia gigas (Ackermann and List, 1959a and b) and later in
the cnidarian Briareum (Ciereszko et al., 1961) and that trimethyltaurine is also found in Geodia gigas (Ackermann and List, 1959a and
b).
111. FUNCTION
When taurine was discovered in the mammalian liver it was thought
to be an excretory product from the breakdown of sulphur-containing
acid in the bile. In fact, it was conjugated with eholic acid in the bile
forming taurocholic acid. Haslewood and Wootton (1950) in a eomparative study of bile salts, found taurine to be a conjugate in the bile
of teleosts, snakes and some mammals, In other mammals, glycine was
the conjugate and sometimes both glycine and taurine occurred
together. In elasmobranchs and amphibia, sulphate is the conjugate.
Bile salts facilitate the emulsification of fats and because of their
ability to form water soluble complexes with fatty acids they help in
the absorption of free fatty acids. Apparently taurine does not have
this function in invertebrates, although Vonk (1960) claimed a bile
227
present in Asterias but as yet undetected. The only proof that in
invertebrates taurine gives rise to taurocyamine has been given by
Abbott and Awapara (1960). Following the injection of high specific
activity S35 taurine into Areniwla they were able to detect after 12 h a
slight amount of radioactivity in the taurocyamine. In vitro, and in one
case, they showed transamidination between arginine and taurine with
the formation of a small amount of taurocyamine (p. 225) Transamidination betwecn arginine and hypotaurine, giving hypotaurocyamine
(2-guanidoethanesulphinic acid) with subsequent oxidation to taurocyamine has been shown to occur in Areniwla and Phaswlosoma
(Thoai et a,!., 1963). In Areniwla, transamidination occurs in the gut
and oxidation in muscle, whereas in Phaswlosoma oxidation occurs in
the gut but not in the muscle of the body wall. As a result, Areniwla
muscle contains ten times as much taurocyamine as hypotaurocyamine,
while the reverse is true of body wall muscle of Phscolosoma. The
inability of the muscle of the body wall of Phaswlosoma to oxidize
hypotaurocyamine is attributed to low external oxygen tension.
Details of the enzymes involved in this pathway are given by Thoai,
1957; Thoai et al., 1963a and b; Thoai and Robin, 1965; Thoai and
Pradel, 1962a and b ; Thoai and Roche, 1960; Kassab et al., 1965;
Hobson and Rees, 1957 ; and Ennor and Morrison, 1958. The metabolic fate of taurocyamine is unknown.
Little is known of the other two derivatives of taurine found in
invertebrates, except that taurobetaine was originally identified in the
sponge Geodia gigas (Ackermann and List, 1959a and b) and later in
the cnidarian Briareum (Ciereszko et al., 1961) and that trimethyltaurine is also found in Geodia gigas (Ackermann and List, 1959a and
b).
111. FUNCTION
When taurine was discovered in the mammalian liver it was thought
to be an excretory product from the breakdown of sulphur-containing
acid in the bile. In fact, it was conjugated with eholic acid in the bile
forming taurocholic acid. Haslewood and Wootton (1950) in a eomparative study of bile salts, found taurine to be a conjugate in the bile
of teleosts, snakes and some mammals, In other mammals, glycine was
the conjugate and sometimes both glycine and taurine occurred
together. In elasmobranchs and amphibia, sulphate is the conjugate.
Bile salts facilitate the emulsification of fats and because of their
ability to form water soluble complexes with fatty acids they help in
the absorption of free fatty acids. Apparently taurine does not have
this function in invertebrates, although Vonk (1960) claimed a bile