Cysteine sulfinate decarboxylase

Some pyridoxal phosphate-dependent enzymes are normally fuUy saturated with cofactor and show the same activity on assay in vitro whether additional pyridoxal phosphate is present in the incubation medium or not. Examples of this class of enzymes include liver cysteine sulfinate decarboxylase (which is involved in the synthesis of taurine from cysteine Section 14.5.1) and the brain and liver glutamate and aspartate aminotransferases. 

The rates of synthesis and cataholism of some pyridoxal phosphate-dependent enzymes are altered in deficiency For example, within a few days of feeding a vitamin Be-free diet to animals, there is a fall in the activity of cysteine sulfinate decarboxylase in fiver after 2 weeks, the amount of the enzyme protein has fallen to extremely low levels. It is Ukely that these enzymes are sacrificed to release pyridoxal phosphate for other, more essential enzymes. Other enzymes show the opposite response - apparent induction of the apoenzyme in vitamin Be deficiency, presumably in an attempt to trap as much of the available pyridoxal phosphate as possible. Sato and coworkers (1996) demonstrated increased cataboUsm of apocystathionase in vitamin Be deficiency, but no decrease in the amount of immunoreactive protein in the liver, as a result of increased transcription. 

Figure 14.7. Pathways for the synthesis of taurine from cysteine. Cysteine sulfinate decarboxylase, EC 4.1.1.29 cysteic acid decarboxylase, EC 4.1.1.29 (glutamate decarboxylase, EC 4.1.1.15) cysteine oxidase, EC 1.13.11.20 cysteamine oxygenase, EC 1.13.11.19 and hypotaurine oxidase, EC 1.8.1.3. Relative molecular masses (Mr) cysteine, 121.2 cysteamine, 77.2 cysteine sulfinic acid, 153.2 cysteic acid, 169.2 hypotaurine, 109.1 and taurine, 125.1.

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. 

Cysteine dioxygenase 2 cysteine sulfinate decarboxylase 3 cysteamine dioxygenase 4 hypotaurine dehydrogenase... 

Pasantes-Iforales, H., Mapes, C., Tapia, R., and Mandel, P., 1976, Properties of soluble and particulate cysteine sulfinate decarboxylase of the adult and the developing rat brain. Brain Res., 107 575-589. 

C. Loriette, H. Pasantes-Morales, C. Portemer and F. Chatagner, Dietary Casein Levels and Taurine Supplementation Effects on Cysteine Dioxygenase and Cysteine Sulfinate Decarboxylase Activities and Taurine Concentration in Brain, Liver and Kidney of the Rat, Nutr. Metab. (in press). 

Oxidation to cysteic acid, followed by decarboxylation to taurine. Cysteic acid and cysteine sulfinic acid decarboxylase activities occur in constant ratio in various tissues, and it is likely that both substrates are decarboxy-lated by the same enzyme. In general, cysteine sulfinic acid is the preferred substrate, and there is little formation of taurine by way of cysteic acid. 

In the liver and brain, the main pathway is by way of cysteine sulfinic acid, whereas in tissues with low cysteine sulfinic acid decarboxylase activity the main precursor of taurine is cysteamine. 

The central nervous system has at least three enzymes capable of decar-hoxylating cysteine sulfonic acid, one of which is glutamate decarboxylase. Glutamate and cysteine sulfinic acid are mumaUy competitive. In some brain regions, more than half the total cysteine sulfinic acid decarboxylase activity may be from glutamate decarboxylase. 

Taurine is a dietary essential in the cat, which is an obligate carnivore with a limited capacity for taurine synthesis from cysteine. On a taurine-free diet, neither supplementary methionine nor cysteine will maintain normal plasma concentrations of taurine, because cats have an alternative pathway of cysteine metabolism reaction with mevalonic acid to yield felinine (3-hydroxy-1,1-dimethylpropyl-cysteine), which is excreted in the urine. The activity of cysteine sulfinic acid decarboxylase in cat liver is very low. 

It is not known to what extent taurine may be a dietary essential for human beings. There is little cysteine sulfinic acid decarboxylase activity in the human liver and, like the cat, loading doses of methionine and cysteine do not result in any significant increase in plasma taurine. This may be because cysteine sulfinic acid can also undergo transamination to /3-sulfhydryl pyruvate, which then loses sulfur dioxide nonenzymically to form pyruvate, thus regulating the amount of taurine that is formed from cysteine. There is no evidence of the development of any taurine deficiency disease under normal conditions. 

Lin C-T, Li J-Z, Wu J-Y (1983) Immunocytochemical localization of L-glutamate decarboxylase, gamma-aminobutyric acid transaminase, cysteine sulfinic acid decarboxylase, aspartate aminotransferase and somatostatin in rat retina. Brain Res 270 273-283. 

Fig. 130. Schematic summary of cysteine sulfinic acid decarboxylase (CSADCase)-positive sagittal microzones or bands in mouse cerebellum. The bands are clearest in the anterior lobe and the vermis, less sharply defined in the hemispheres (dense stipple), and most difficult to discern in the paraflocculus and flocculus (light stipple), because of intense CSADCase reactivity in most Purkinje cells. The dentate (D), interpositus (I), fastigial (F), and lateral vestibular nuclei (LVN) contain numerous CSADCase-positive cells. Chan-Palay et al. (1982b).

Chan-Palay V, Lin CT. Palay SL, Yamamoto M, Wu J-Y (1982a) Taurine in the mammalian cerebellum demonstration by autoradiography with tritiated taurine and immunocytochemistry with antibodies against the taurine synthesizing enzyme, cysteine sulfinic acid decarboxylase. Proc. Natl. Acad. Sci. USA, 79, 2695-2699. 

Magnusson KR, Madl JE, Clements JR, Wu J-Y, Larsson AA, Beitz, AJ (1988) Colocalization of taurine-and cysteine sulfinic acid decarboxylase-like immunoreactivity in the cerebellum of the rat with monoclonal antibodies against taurine. J. Neurosci.. 8, 4551 564. 

Fig. 20.3 Pathway of methionine metabolism. The numbers represent the following enzymes or sequences (1) methionine adenosyltransferase (2) S-adenosylmethionine-dependent transmethylation reactions (3) glycine methyltransferase (4) S-adenosylhomocysteine hydrolase (5) betaine-homocysteine methyltransferase (6) 5-methyltetrahydrofolate homocysteine methyltransferase (7) serine hydroxymethyltransferase (8) 5,10-methylenetetrahydrofolate reductase (9) S-adenosylmethionine decarboxylase (10) spermidine and spermine synthases (11) methylthio-adenosine phosphorylase (12) conversion of methylthioribose to methionine (13) cystathionine P-synthase (14) cystathionine y-lyase (15) cysteine dioxygenase (16) cysteine suplhinate decarboxylase (17) hypotaurine NAD oxidoreductase (18) cysteine sulphintite a-oxoglutarate aminotransferase (19) sulfine oxidase. MeCbl = methylcobalamin PLP = pyridoxal phosphate...

Wu J.-Y. (1982) Purification and characterization of cysteic/cysteine sulfinic acids decarboxylase and L-glutamate decarboxylase in bovine brain Proc Natl Acad. Sci. USA 79, 4270-4274... 

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... 

The latter is decarboxylated by the action of cysteic decarboxylase and the oxidized sulfur is excreted in the form of taurine. At that time it is of interest to compare the action of desulfinicase with the action of decarboxylase. There seems to exist a certain analogy between these enzymes, just as there is an analogy between the sulfinic and carboxyl groups on which they act. But the experiments carried out to date do not show whether the desulfinicase acts by splitting off sulfur dioxide from cysteine sulfinic acid according to the equation ... 

Cysteinesulfinic Acid. Cysteine is oxidized by enzyme systems present in bacteria and in liver to the corresponding sulfinic acid. It has been suggested that the unstable sulfenic acid is an intermediate in this oxidation. The nature of the reaction that produces cysteinesulfinic acid is not known. The subsequent metabolism of the sulfinic acid may proceed by any of three pathways. One involves further oxidation to cysteine-sulfonic acid, cysteic acid. The enzyme responsible has not been separated from the system responsible for the formation of cysteinesulfinic acid. Cysteinesulfonic acid is decarboxylated to taurine (I) by the decarboxylase mentioned previously (p. 284). 

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