Taurine synthesis in teleost-importance of cysteamine pathway
Keywords:
Taurine, Synthesis, TeleostsAbstract
Taurine plays various roles in animals such as growth promotion, osmoregulation, bile acid conjugation,
neurotransmission, cardiac muscle contraction, antioxidant activity, and reproduction. Taurine is one of the
essential nutrients for marine fish larvae and in fishes which lack endogenous taurine production. Taurine is
synthesized from methionine via cysteine. Cysteine is converted to cysteine sulfinic acid by activity of cysteine
dioxygenase (CDO) and cysteine sulfinic acid is converted into hypotaurine by cysteine sulfinic acid
decarboxylase (CSD) in CSD pathway which is considered to be a major taurine production pathway in fish.
Hypotaurine is finally converted into taurine by auto-oxidation. In addition to CSD pathway, there is two other
taurine synthetic pathways are know: cysteic acid pathway where cysteine is oxidized into cysteic acid, and it is
directly converted into taurine by cysteic acid decarboxylase (CAD) activity and cysteamine pathway where
cysteine is converted into cysteamine and it is converted into hypotaurine by cysteamine dioxygenase (ADO).
However, detail on taurine production by these two pathways is not understood.
Common carp is widely cultured in the world and world production of cypriniforms is highest among food fish
species. Rainbow trout is known to have sufficient CSD activity to produce taurine via methionine. In contrast,
it was reported that CSD activity in common carp is about half of that reported in rainbow trout. However,
common carp did not show growth retardation when it was fed taurine deficient diet. These observations led
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Haga, Y. et al., 2017.Taurine synthesis in teleosts-importance of cysteamine pathway. En: Cruz-Suárez, L.E., Ricque-Marie, D., Tapia-Salazar, M., Nieto-López, M.G.,
Villarreal-Cavazos, D. A., Gamboa-Delgado, J., López Acuña, L.M. y Galaviz-Espinoza, M. . (Eds), Investigación y Desarrollo en Nutrición Acuícola Universidad Autónoma de Nuevo
León, San Nicolás de los Garza, Nuevo León, México, pp. 264-283. ISBN 978-607-27-0822-8.
hypothesis that common carp is able to produce sufficient amount of taurine beside the CSD pathway. The
purpose of the present study is to investigate effect of dietary supplementation of cysteine, cysteamine,
methionine, and taurine on the growth, sulfur amino acid content, and gene expression of taurine synthesizing
enzymes.
Eight different diets supplemented with taurine, methionine, cysteine, and cysteamine were fed to the juvenile
common carps for 30 days. For control, a diet without supplying sulfur amino acid was fed. Feeding diets
supplemented sulfur amino acid resulted in better survival, growth, feed conversion ratio, and protein efficiency
ratio except treatments supplemented with cysteamine. It was observed that the supplementation of dietary
cysteamine caused growth retardation, myopathy, and body deformity in common carp. All sulfur amino acids
increased taurine deposition in the carcass and 1.5% cysteamine increased taurine deposition by 1.8 and 5.5
times higher than those of the methionine and cysteine treatments. CDO was tended to be down-regulated by
cysteine and low dose of taurine but up-regulated by a high dose of cysteamine. It was observed that CSD was
down-regulated by sulfur amino acids. ADO was down-regulated by methionine, cysteine and low dose of
taurine but up-regulated by cysteamine.
These results suggest that CSD pathway plays a role in taurine synthesis and cysteamine pathway is another
major taurine synthesizing pathway in common carp.
