Cysteine Oxidase Research Articles

Subcellular distribution of cysteine oxidase activity in ox retina

Cysteine oxidase activity has been determined in the primary and secondary subfractions of ox retina. About 30% of enzyme activity is found in the soluble fraction while about 70% is associated with particulate components. In the secondary subcellular fractions about 36% of enzyme activity, recovered from crude mitochondria, is present in the synaptosomal fraction. Enzymic activity is stimulated by Fe ++ and NAD +. The reason and significance of the cysteine oxidase activity in synaptosomal fraction are briefly discussed in relation with taurine function in retina.

Purification and some properties of rat liver cysteine oxidase (cysteine dioxygenase)

Cysteine oxidase (cysteine dioxygenase, EC 1.13.11.20) was purified approximately 1000-fold from rat liver. The purified enzyme (protein-B) was obtained as an inactive form, which was activated by anaerobic preincubation with l-cysteine. The active form of protein-B was inactivated during aerobic incubation to produce cysteine sulfinate. This inactivation of protein-B was protected by a distinct protein in rat liver cytoplasm, namely stabilizing protein (protein-A). The K a and K m values for l-cysteine were 0.8·10 −3 M and 1.3·10 −3 M respectively. The enzyme was strongly inhibited by Cu + and/or Fe 2+ chelating agents but not by Cu 2+ chelating agent. The optimum pH of enzyme reaction was 8.5–9.5 while that of enzyme activation was 6.8–9.5, with a broad peak.

Cysteine oxidase in brain

Cysteine oxidase, which catalyzes the oxidation of cysteine to the neuroexcitatory and neurotoxic compounds cysteine sulfinic and sulfonic acids, previously has not been studied successfully in brain. Here we report optimal conditions for measuring cysteine oxidase activity in rat brain, describe its regional and subcellular distribution and compare activity during several stages of development. Employing NAD+ as cofactor, substantial activity was measurable in whole brain homogenate, 70% of which was localized to the microsomal fraction. Appreciable activity was present throughout brain with a 3-fold difference being detected between pons-medulla and cerebral cortex, the regions with the highest and lowest levels respectively. Cysteine oxidase activity in adult rat brain was approximately 5 times higher than that measured at birth. For the first 6 days of life there was very little change in activity; thereafter, a steady increase occurred with adult levels being reached between the 25th and 50th days.

Cysteine-S-sulfate: brain damaging metabolite in sulfite oxidase deficiency.

Cysteine-S-sulfate is an abnormal metabolite discovered in the urine and blood of a patient with cysteine oxidase deficiency, a rare disorder of sulfur amino acid metabolism associated with brain damage and mental retardation. The molecular structure of cysteine-S-sulfate closely resembles that of glutamate and related acidic amino acids which have both neuroexcitatory and neurotoxic properties (excitotoxic amino acids). Here we demonstrate that cysteine-S-sulfate induces the glutamate type of neuropathology in the rat central nervous system when administered subcutaneously to infants or intracerebrally to adults. It is postulated that cysteine-S-sulfate may be the neurotoxic agent responsible for brain damage in sulfite oxidase deficiency. The possibility that other excitotoxic amino acids could play occult roles in other unexplained neuropathologic conditions is discussed.

Cysteine oxidase activity in rat retina during development

Cysteine oxidase activity has been determined in developing rat retina. Enzymic activity is present in 55, 000 × g supernate and in the crude mitochondria. Activity is rather low at birth; but increases with age; in mitochondria it reaches its maximum value at the 25th day while in supernate it increases more rapidly, reaching its maximum value 20 days after birth; unlike in the mitochondria, the activity of supernate considerably decreases during further development. The reason and significance of the postnatal changes in the mitochondrial cysteine oxidase activity are briefly discussed in relation with taurine formation.

Two components of cysteine oxidase in rat liver

Purified cysteine oxidase in rat liver is composed of two distinct proteins. These proteins are able to be fractionated by DEAE-cellulose column chromatography. It appears that one of them is a catalytic protein named protein-B having tightly bound iron as a prosthetic group, while the other is either a modifier or activating protein named protein-A. Protein-B is found to exist in both an active and an inactive form. Inactive protein-B is activated by incubation with substrate cysteine under anaerobic condition. Activated protein-B alone exhibited an extremely low catalytic activity but in the presence of protein-A remarkable increase in activity was observed.

Induction and activation of cysteine oxidase of rat liver II. The measurement of cysteine metabolism in vivo and the activation of in vivo activity of cysteine oxidase

1. 1. The incorporation of 14C into expired CO 2 from DL-[3- 14C]cysteine injected intraperitoneally into rats was slightly decreased by a loading dose of D-cysteine, whereas either the incorporation from DL-[1- 14C]cysteine or L-[U- 14C]-cysteine was unaffected by this loading. 2. 2. The incorporation of 14C into CO 2 from DL[1- 14C]cysteine or L-[U- 14C]-cysteine was remarkably elavated by L-cysteine loading. 3. 3. Hepatic cysteine oxidase activity was markedly induced by L-cysteine injection but cysteine desulfhydrase activity was not affected. 4. 4. The expected maximum 14CO 2 expirations expressed as C max and the C max half-times for DL-[1- 14C]cysteine, DL-[3- 14C]cysteine and L-[U- 14C]cysteine injected were calculated from the kinetics of 14CO 2 expiration as a function of time. 5. 5. The metabolic distributions of L-cysteine catabolism was calculated from these C max values; L-cysteine is metabolized 31% via the pyruvate pathway and 69% via the taurine pathway. 6. 6. Urinary excretion of 35S from L-[ 35S]cysteine injected was also examined. 7. 7. The facts presented in this paper strongly suggest that the degradation of L-cysteine is metabolized mainly through cysteine sulfinate, and therefore the incorporation of 14CO 2 into expired CO 2 from L-[U- 14C]cysteine is a reflection of the in vivo activity of cysteine oxidase and that the in vivo activity of cysteine oxidase was markedly enhanced by L-cysteine loading but not by D-cysteine loading.

Induction and activation of cysteine oxidase of rat liver: I. The effects of cysteine, hydrocortisone and nicotinamide injection on hepatic cysteine oxidase and tyrosine transaminase activities of intact and adrenalectomized rats

1. 1. The greatest increase in hepatic cysteine oxidase activity was observed in intact rats which received cysteine, but the increase in tyrosine transaminase activity mediated by cysteine was only one-half of that produced with nicotinamide or hydrocortisone. 2. 2. The decline of the elevated enzymic activity of either cysteine oxidase or tyrosine transaminase was delayed when these enzymes were induced by nicotinamide in intact rats. 3. 3. An additive increase in cystein oxidase activity in the intact rat was obtained by the simultaneous injection of nicotinamide with cysteine and of nicotinamide with hydrocortisone but not of cysteine with hydrocortisone. 4. 4. Hepatic cysteine oxidase and tyrosine transaminase activities in adrenalectomized rats were significantly increased after injection of hydrocortisone but not by cystein. Nicotinamide did produce a marked increase in tyrosine transaminase activity in adrenalectomized rats, while cysteine oxidase activity did not increase with either nicotinamide or cysteine. The hydrocortisone-mediated induction of hepatic cysteine oxidase activity was markedly enhanced by simultaneous injection of cysteine, but in the case of hepatic tyrosine transaminase activity, the hydrocortisone-mediated induction was not affected by cysteine injection. 5. 5. Cysteine-mediated induction of hepatic cysteine oxidase was partially inhibited by the simultaneous injection of cycloheximide, whereas hydrocortisone- and nicotinamide-mediated inductions were completely inhibited by cycloheximide.

Cysteine oxidation and annulment of amphotericin B inhibition of Coccidioides immitis.

The capacity of cysteine to annul the inhibitory action of amphotericin B on Coccidioides immitis was studied. Concomitant with inhibited growth were suppressed respiration patterns. Added cysteine, however, which was not oxidized by untreated endospores, was attacked by amphotericin-treated cells; it was oxidized to cystine. A crude cysteine oxidase was obtained from endospores that had not been exposed to cysteine. Evidence is presented that exogeneous cysteine is oxidized by endospores only after amphotericin damages cell barriers. It is speculated that the resulting oxidation is an important feature in the annulment of amphotericin activity.

Intermediary metabolism of cysteinesulfinic acid in cell-free extracts of Proteus vulgaris

1.1. The greatest increase in hepatic cysteine oxidase activity was observed in intact rats which received cysteine, but the increase in tyrosine transaminase activity mediated by cysteine was only one-half of that produced with nicotinamide or hydrocortisone.2.2. The decline of the elevated enzymic activity of either cysteine oxidase or tyrosine transaminase was delayed when these enzymes were induced by nicotinamide in intact rats.3.3. An additive increase in cystein oxidase activity in the intact rat was obtained by the simultaneous injection of nicotinamide with cysteine and of nicotinamide with hydrocortisone but not of cysteine with hydrocortisone.4.4. Hepatic cysteine oxidase and tyrosine transaminase activities in adrenalectomized rats were significantly increased after injection of hydrocortisone but not by cystein. Nicotinamide did produce a marked increase in tyrosine transaminase activity in adrenalectomized rats, while cysteine oxidase activity did not increase with either nicotinamide or cysteine. The hydrocortisone-mediated induction of hepatic cysteine oxidase activity was markedly enhanced by simultaneous injection of cysteine, but in the case of hepatic tyrosine transaminase activity, the hydrocortisone-mediated induction was not affected by cysteine injection.5.5. Cysteine-mediated induction of hepatic cysteine oxidase was partially inhibited by the simultaneous injection of cycloheximide, whereas hydrocortisone- and nicotinamide-mediated inductions were completely inhibited by cycloheximide.