It is fairly common knowledge that domesticated cats cannot synthesize the compound taurine. Other mammals seem to be able to synthesize taurine from cysteine [source]. Are there other mammals that lack the ability to synthesize taurine?
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1$\begingroup$ Apparently cats can synthesize taurine from cysteine by the action of cysteine dioxygenase type 1 (CDO1) and glutamate decarboxylase 1 like (GADL1)/GAD2 enzymes. You can find out which organisms cannot synthesize taurine from cysteine from here. I don't know how to parse this data at this moment and I don't have the patience to manually check. $\endgroup$– WYSIWYGApr 27, 2016 at 18:30
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1$\begingroup$ @WYSIWYG The Kegg map for taurine metabolism is here but if you compare felis catus with canis familiaris you find no differences in the enzymes supposedly present. If correct, this is consistent with Gwen's post. $\endgroup$– DavidApr 28, 2016 at 9:35
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$\begingroup$ @David Yes. Possibly the enzymes exist but are deficient. $\endgroup$– WYSIWYGApr 28, 2016 at 9:47
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It is a misconception that cats cannot synthesize taurine.
Cats can synthesize taurine, just like other mammals, but not enough of it to make up for an entirely taurine-deficient diet. Cats (and other mammalian carnivores) would have consumed a taurine-rich diet in the ancestral environment. It is only when they are fed vegetable/fruit/grain-derived foods that they show symptoms of taurine deficiency--because those foods have low quantities of taurine and other taurine precursors.
Other domesticated or captive carnivorous mammal species are at risk of taurine-deficiency if they are fed vegetable-derived foods, though members of the cat family (Felidae) are particularly susceptible.
Primary reference: This 2003 paper about taurine concentrations in animal feed, especially the 'Discussion' section.
Taurine is an essential nutrient of cats because the rate of taurine synthesis from its dietary sulphur amino acid precursors, cysteine and methionine, is much less than the extent of loss through faecal bile acids and urine (Knopf et al., 1978). From an evolutionary standpoint, taurine was plentiful in the diet of a true carnivore, as high concentrations of taurine are found in muscle tissue. However, as most domesticated felines normally do not consume living prey, they are at risk to become taurine-deficient if not adequately supplied in the diet.
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$\begingroup$ This would be consistent with the Kegg entries for enzymes of taurine metabolism for dog and cat, as I mention in my comment on the question. $\endgroup$– DavidApr 28, 2016 at 9:37
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$\begingroup$ Perhaps you can give an example of a mammal that can actually not synthesize taurine i.e. it lacks the enzymes. $\endgroup$– WYSIWYGApr 28, 2016 at 9:49
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