Cysteamine hypotaurine

The experimental results reported demonstrate that in beef kidney cortices is present a small protein operating a one-side decarboxylation of lanthionine with the production of aminoethylcysteine which is furtherly degraded into cysteamine,hypotaurine and taurine as previously reported(21).At the present time cannot be claimed that this decarboxylase is specific toward lanthionine its activity on lanthionine could be an ancillary activity of another decarboxylase.However this activity on lanthionine demonstrate the presence in animal tissues of a new route which,via cysteamine,contributes to taurine pool.These results further confirm that cysteamine pathway appears to be the most important route... 

This enzyme [EC 1.13.11.19] catalyzes the reaction of cysteamine with dioxygen to produce hypotaurine. The protein uses iron ions as cofactors. 

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.

In this section we examine structurally complex thiazines, where the heterocycle forms part of a polycyclic system. Many of these fascinating natural products also contain quinone chromophores, and in many cases the corresponding compound lacking the thiazine ring also occurs in Nature. Hence it appears that the thiazine ring is added late in the biosynthetic pathway, presumably by addition of cysteine, cysteamine or hypotaurine to the quinone. 

Cavallini, D., C. De Marco, R. Scandurra, S. Dupr, and M. T. Graziani The Enzymatic Oxidation of Cysteamine to Hypotaurine. J. Biol. Chem. 241, 3189 (1966). Rotilio, G., G. Frederici, L. Calabrese, M. Costa, and D. Cavallini An Electron Paramagnetic Resonance Study of the Nonheme Iron of Cysteamine Oxygenase. J. Biol. Chem. 245, 6235 (1970). 

Cysteamine is oxidized by cysteamine dioxygenase (EC 1.13.11.19) to hypotaurine, which is then oxidized to taurine by an as yet unidentified enzyme. 

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

Sulfinic acids, e.g., L-cysteine sulfinic acid and hypotaurine, and sulfonic acids, e.g., L-cysteic acid and taurine, are naturally occurring products of L-cysteiiie and cysteamine oxygenation. They occur in microorganisms, plants, and animals. 

L-Cysteine is transformed to L-cysteine sulfinic acid and L-cysteic acid. Cysteamine (D 11) yields hypotaurine and taurine (Fig. 189). The latter compounds may be transformed to other secondary products by deamination, thiolation, guanylation, and methylation. L-Cysteine sulfinic acid may be degraded to L-alanine and sulfurous acid, which is oxidized to sulfuric acid. 

The free amino acid fraction also contains 0.02-0.1% taurine (I). As such, taurine should be regarded as a major constituent of this fraction. It is obtained biosynthetically from cysteine through cysteic acid and/or from a side pathway involving cysteamine and hypotaurine (II) ... 

This amine is apparently not formed by a direct decarboxylation of cysteine. An enzymic decarboxylation and reduction of cystine disulfoxide, a potential precursor of cysteamine [Eq. (4)], is only a hypothetical pathway at present. The pantetheine moiety of coenzyme A may, however, yield cysteamine in vivo ( 8). Cysteamine in vivo and in vitro is partly transformed to hypotaurine ( 9) and its S appears as SOr in the urine. An interesting property of this amine is its powerful protecting action in vivo against lethal doses of X-rays. 

Fig. 1 CYSTEAMINE OXYGENASE ACTIVITY IN HUMAN LIVER 30 mg of human liver homogenate, j> tained by biopsy, were incubated, as reported in the text, with S-cysteamine in the presence of cofactor. A = zero time, B = 4 hours incubation. The radioactive peaks correspond to taurine (l), hypotaurine (2) and unreacted cysteamine (3).

S-cysteamine, in the presence of phenazine methosulfate. After 4 hours incubation about 50% of cysteamine is oxidized to hypo-taurine and taurine. The same result is obtained if the activity is performed in the absense of phenazine. This result is unexpected since usually the activity in the presence of cofactor is between three or five times higher than in the absence. This particular aspect merit to be investigate further in order to examine whether a natural compound is present in human liver acting as cofactor for cysteamine oxygenase. Moreover, as shown in fig. 1, a consistent portion of hypotaurine is recovered oxidized to TAU. 

However, as far as the biosynthesis is considered, the cysteinesulfinic (CSA) pathway and the cysteamine pathway are considered as prevalent each tissue showing a preference for the one of the other route In this respect, it is of interest that in these both pathways the intermediate metabolite formed is hypotaurine 5 The metabolism of hypotaurine is not clearly known, although the oxidation of hypotaurine into taurine is... 

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