Cysteine dioxygenase

Dominy JE, CR Simmons, PA Karpins, AM Gehring, MH Stipanuk (2006) Identification and characterization of bacterial cysteine dioxygenases a new route of cysteine degradation for eubacteria. J Bacteriol 188 5561-5569. 

Interestingly, cysteine dioxygenase, among a growing number of other iron(ll) oxygenases, has the carboxylate residue replaced by another histidine. 

A number of enzymes involved in cysteine metabolism have been described in the tapeworm Hymenolepis diminuta (48). In addition to a high cystathionine /3-synthase activity it has low y-cystathionase activity, and contains cysteine aminotransferase, cysteine dioxygenase and cysteine sulphinate aminotransferase the latter two could be involved in the oxidation of cysteine. 

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...

The cysteinesulphinic acid pathway starts with the oxidation of cysteine by cysteine dioxygenase (EC 1.13.11.20). In the rat, cysteine dioxygenase is found only in the fiver and consists of two sub-units containing Cu and Fe, one catalytic and the other... 

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

CYSTEINE DIOXYGENASE OF RAT LIVER SOME PROPERTIES AND ITS SIGNIFICANCE ON CYSTEINE IffiTABOLISM OF RAT... 

Cysteine dioxygenase was purified from rat liver cytoplasm to homogeneity. A summary of the purification procedure is given in Table 1. 

Table 1. Summary of purification of rat liver cysteine dioxygenase...

Effects of temperature and of the concentration of L-cysteine on the anaerobic activation of cysteine dioxygenase. A, Cysteine dixoygenase was preincubated with 10 mM L-cysteine under anaerobic condition at 10, 20, 30 and 37 , and the volume of preincubation mixture was 0.05 ml. B, Cysteine dioxygenase was preincubated under normal activation conditions except the concentration of L-cysteine given in the figure, and the volume of preincubation mixture was 0.05 ml. After mixture volume was adjusted to 1.0 ml, the enzyme activity was assayed under standard assay con-citions. (From Yamaguchi et al., ref. 13, with permission)... 

Possible conformational change of cysteine dioxygenase by activation... 

Table 2. Inhibition by chelating agent and trypsin inactivation of activated cysteine dioxygenase...

Induction of cysteine dioxygenase in rat liver by methionine and cysteine... 

We have found that cysteine oxidase activity in rat liver, which was assayed by NAD-depending assay system , was induced by either cysteine or methionine in the presence of permissive amounts of glucocorticoids. Recently, we have reexamined the effect of cysteine or methionine injection on the cysteine dioxygenase activity assayed by the new assay method as mentioned above. As shown in Table 3, the hepatic cysteine dioxygenase activity was also remarkably increased by the intraperitoneally injected cysteine or methionine. On the other hand, the increase of enzyme activity mediated by cysteine or methionine was not observed in adrenalectomized rat. 

Table 3. Effects of hydrocortisone, L-cysteine, L-methionine on the rat liver cysteine dioxygenase activity...

Fig. 4. The effects of dietary protein on the activities of cysteine dioxygenase, cysteine desulfhydrase in liver and the urinary taurine excretion of intact rat. Plotted are cysteine dioxygenase activity(0). Cysteine desulfhydrase activity (O )> urinary taurine contents (I j). Results are expressed as the mean S.D.(represented by vertical line) of six and three animals fed on basal diet (20% protein diet) and other diets, respectively. Animals were fed on experimental diets for 2 days prior to sacrifice.

CYSTEINE. DIOXYGENASE ACITIVITY OF RAT LIVER DURING DEVELOPMENT... 

Fig. 5 summarizes the relationship between cysteine dioxygenase activity in rat liver with or without hydrocortisone injection and the hepatic cysteine contents during development. No significant activity was detected in fetal and postnatal rat liver younger than 4-day-old, and first appeared in detectable levels at the 8th postnatal day. The enzyme activity gradually increased to 13% of the adult level by 12-day-old and then markedly increased to reach the adult level at the 28th postnatal day. 

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