16.5.2 Bile Salts of Individual Animal Groups
649
Cholesterol
70.- Hydroxy- 4-cholesten -3 -one
5~ - Cholestan - 30.,7 0.- diol
5~-Cholestan -30.,70., 12a-triol
50. - Cholestan - 30.,70.,120. - triol
HO"
(Tauro-)
Chenodeoxycholic acid
Lithocholic acid
(Tauro-)
Cholic acid
Deoxycholic acid
Fig. 16.17 • The biosynthesis of bile acids and alcohols [25].
The taurine conjugation is shown only for chenodeoxycholic acid and cholic acid. 1, 7a-Hydroxylation; 2, oxidation at C-3 and /).5//).4 isomerization; 3, 12a-hydroxylation;
4a, /).4-3-oxosteroid-5a reduction; 4b, /).4-3-oxosteroid-5~
The lung fish (Dipnoi) are distributed over
three continents; Lepidosiren paradoxa is found
in South America, Neoceratodus Josteri exists in
Australia, and the four species of Protopterus are
~I
50. - Cyprinol
OH
OH
reduction; 5, oxidative cleavage of the side-chain at C-24 as
propionyl-CoA; 6, conjugation with taurine (or glycine);
7,26- and 27-hydroxylation; 8, formation of secondary bile
acids by gut bacteria
found in Africa. Nevertheless, the bile salts of the
Dipnoi are all very similar. 27-Deoxy-5a-cyprinol
is found in all three, 5a-cyprinol in Protopterus
and Lepidosiren, and 5a-bufol in Lepidosiren and