Hypotaurine oxidase

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.

According to a recent report hypotaurine is oxidized into taurine by ultraviolet irradiation, which suggests that a non enzymatic oxidation could occur on the other hand, an enzymic oxidation of hypotaurine into taurine, catalysed by hypotaurine oxidase, was described in various tissues of the rat 7 and in the retina of different species 8, in view of the poor knowledge which still exists about the metabolism of hypotaurine and especially about its enzymic oxidation into taurine, we decided to initiate experiments in order to contribute to a better understanding of this last step. 

The values are the mean SEM of 3 experiments in each case. The concentration of taurine is expressed in ymoles of taurine/g wet tissue and the activity of hypotaurine oxidase in ymoles/h/g wet tissue. 

Di Giorgio, R. M., Macaione, S., and De Luca, G., 1977, Subcellular distribution of hypotaurine oxidase activity in ox retina. 

Table V, Hypotaurine oxidase activity in primary and secondary subcellular fractions from ox retina...

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...

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