Cysteamine oxygenase activity

In this context it is important to examine the tissue levels of cysteine oxygenase and cysteamine oxygenase activities in order to distinguish, if possible, the relative contribution of CSA pathway and cysteamine pathway in TAU biosynthesis. 

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. 

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