Taurine biosynthesis

FIGURE 2.40 The major pathway for taurine biosynthesis in the liver- First, cy teine is converted to cysteine sulfinic acid in an oxygen-requiring reaction catalyzed by an iron metalloeozyme- The second step, catalyzed by a vitamin B -requiring enzyme, is a decarboxylation reaction. The final step appears to be catalyzed by a copper metaLloenzyme and to require oxygen. Apparently, about one-fourth of the cysteine in the liver eventually is converted to taurine. 

Almarghini K, Remy A, Tappaz M (1991) Immunocytochemistry of the taurine biosynthesis enzyme, cystein sulfinate decarboxylase, in the cerebellum Evidence for a glial localization. Neuroscience, 43, 111-119. 

The essentiality of cysteine for the fetus and newborn may underlie their low or nonexistent ability to convert cysteine to taurine, another low molecular weight sulfur containing confound apparently required in large amounts by developing brain (Sturman et al., 1978). The supply of cysteine may all be required for protein synthesis and none spared for taurine formation. Cystelnesulflnic acid decarboxylase (EC 4.1.1.12), the enzyme chiefly responsible for taurine biosynthesis in mammals, develops slowly after birth and reaches maximum activity in mature brain (Agrawal et al.,1971 Pasantes-Morales et al.,1976 Rassin et al., 1979), although the concentration of taurine decreases over this same period (Fig. 4). Cystelnesulflnic acid decarboxylase also uses pyridoxal 5 -phosphate as coenzyme, and is extremely sensitive to a dietary deficiency of vitamin Bg (Hope, 1955 Rassin and Sturman, 1975). 

Taurine Biosynthesis Hypotaurine Cysteine sulfinic acid Cysteine... 

D. Cavallini, R. Scandurra, S. Duprg, S. Santoro and D. Barra, A New Pathway of Taurine Biosynthesis, Physiol. Chem. Phys. 8 157 (1976). 

Several metabolic pathways can lead to taurine biosynthesis (35), The most Important route In mammalian tissues. Including brain and retina, has been shown to originate by pathway I (methionine—>cysteine —>cystelne sulphinate — hypotaurlne—>taurlne),... 

In the present chapter we will report the subcellular distribution pattern of taurine and enzymatic activities involved in taurine biosynthesis in ox retina and in particular in the subcellular nuclear fraction which contains besides nuclei, the outer and inner segments of photoreceptors as well as pinched-off nerve-endings of the photoreceptors. 

In ox retina, similarly to other vertebrate retinas studied, the highest content in taurine was found at the photoreceptor level (unpublished data). The existence of the enzymic activities leading to taurine biosynthesis in photoreceptors exclude that taurine uptalanimal species, responsible for taurine accumulation at this level. 

G. Ricci, and D. Barra, Alternative pathways of taurine biosynthesis, ij2 "T aurine", R. Huxtable and A. Barbeau eds., Raven Press. New York (1976). 

The problem of regulation is complicated by the metabolic complexity of sulfur amino acids, and the wide variation in organ taurine concentrations between species. The major putative metabolic routes to taurine from cysteine are three These involve the intermediacy respectively of cysteine sulfinic acid, cysteic acid, and cysteamine. The first two utilize the enzyme cysteine sulfinic acid decarboxylase (CSAD), and the latter the enzyme cysteamine dioxygenase (CD). The distribution of these enzymes differ both quantitatively and qualitatively in corresponding organs of various species. Other pathways of taurine biosynthesis have also been proposed. For... 

Cavallini,D.,Scandurra,R.,Dupre,S.,Federici,G.,Santo-ro,L.,Ricci,G.and Barra,D."Alternative pathways of taurine biosynthesis"in"Taurine"Huxtable,R.and Barbeau A.ed.Raven Press,New York(1976). 

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