Cysteic Acid Decarboxylase Research Articles

Birth of a pathway for sulfur metabolism in early amniote evolution.

Among amniotes, reptiles and mammals are differently adapted to terrestrial life. It is well appreciated that terrestrialization required adaptive changes of vertebrate metabolism, particularly in the mode of nitrogen excretion. However, the current paradigm is that metabolic adaptation to life on land did not involve synthesis of enzymatic pathways de novo but repurposing of existing ones. Here, by comparing the inventory of pyridoxal phosphate-dependent enzymes (PLPome) in different amniotes, we identify in silico a pathway for sulfur metabolism present in chick embryos but not in mammals. Cysteine lyase (CL) contains heme and PLP cofactors and converts cysteine and sulfite into cysteic acid and hydrogen sulfide. A specific cysteic acid decarboxylase (CAD) produces taurine while hydrogen sulfide is recycled into cysteine by cystathionine beta-synthase (CBS). This reaction sequence enables the formation of sulfonated amino acids during embryo development in the egg at no cost of reduced sulfur. The pathway originated around 300 million years ago in a proto-reptile by CBS duplication, CL neofunctionalization, and CAD co-option. Our findings indicate that adaptation to terrestrial life involved innovations in metabolic pathways and reveal the molecular mechanisms by which such innovations arose in amniote evolution.

GABA and Taurine Enzymes in Mammalian Brain

γ -Aminobutyric acid (GABA) and taurine are two structurally related amino acids and both have been proposed as inhibitory neurotransmitters or modulators in the mammalian central nervous system. This chapter describes the purification procedures and basic physicochemical and kinetic properties of L-glutamate decarboxylase (GAD), GABA-transaminase (GABA-T), and cysteine sulfinate decarboxylase (CSAD)/ cysteic acid decarboxylase (CAD). The chapter also discusses the species, tissue, and cell specificities of GAD, GABA-T, and CSAD/CAD. GAD and GABA-T were purified from mouse brain by first extracting the enzymes from crude mitochondrial fraction, followed by ammonium sulfate fractionation and a combination of gel filtration, calcium phosphate gel, and DEAE-Sephadex column chromatographies. Eleven steps were employed in the purification of GAD and approximately 1.2% of the total activity was recovered as a purified enzyme preparation representing 940-fold purification over the original homogenate. GABA-T was purified 1200-fold over the brain homogenate with a specific activity of 5.0 units/mg of protein. The molecular weight of GAD and GABA-T from mouse brain was obtained as 85,000 ± 2000 and 109,000, respectively, from sedimentation equilibrium. The molecular weight of the human brain GAD was found to be about 100,000 by Sephadex-gel filtration and about 95,000 by sodium dodecyl sulfate -polyacrylamide gel electrophoresis.

Effect of bile acid derivatives on taurine biosynthesis and extracellular slime production in encapsulated Staphylococcus aureus S-7.

Various bile acids were added to cultures of encapsulated strains of Staphylococcus aureus growing in serum-soft agar medium of brain heart infusion broth. We examined effects of these compounds on cellular characteristics such as growth type, cell volume index, clumping factor reaction, slime yield, taurine content, and L-(--)-cysteic acid decarboxylase activity. Upon addition to the medium of either taurochenodeoxycholic acid, taurocholic acid (25 to 50 microgram/ml), or cholic acid (10 to 25 microgram/ml), the colonial morphology of taurine-positive cells (strain S-7) was altered from the diffuse to the compact type in serum-soft agar. Also, the titer of the clumping factor reaction increased, while the cell volume index and slime yield were markedly decreased. Tauro-bile acids, including taurocholic acid, taurochenodeoxycholic acid, taurodehydrocholic acid, and taurodeoxycholic acid (50 microgram/ml) inhibited the synthesis of taurine and resulted in decreased L-(--)-cysteic acid decarboxylase activity. Among all of the derivatives cholic acid itself was found to inhibit slime production and L-(--)-cysteic acid decarboxylase activity to the greatest extent. Glyco-bile acid derivatives and taurolicholic acid (50 to 100 microgram/ml) had no effect on L-(--)-cysteic acid decarboxylase activity. Compounds such as glycodeoxycholic acid (50 to 100 microgram/ml) had no effect upon any of the cellular characteristics tested. No effect was observed upon addition of any of these compounds to cultures of the taurine-negative strain (T-26-B). We did find a correlation between the inhibition of taurine biosynthesis and decreased slime production. Electron micrographs indicated that this encapsulated strain was converted to an unencapsulated state in the presence of bile acids.

Tissue and regional distribution of cysteic acid decarboxylase. A new assay method.

A sensitive and rapid assay method method for cysteic acid decarboxylase was develped which combined the selectivity of ion exchange resin (a complete retention of the substrate, cysteic acid, and exclusion of the product, taurine) with the speed of a vacuum filtration. The synthesis and purification of 35S-labeled cysteic acid were described. The validity of the assay was established by the identification of the reaction product as taurine. With this new method, the decarboxylase activity was measured in discrete regions of bovine brain. Putamen had the highest activity, 172 pmol taurine formed/min/mg protein (100%), followed by caudate nucleus, 90%; cerebral cortex, 82%; hypothalamus, 81%; cerebellar cortex, 79%; cerebellar peduncle, 59%; thalamus, 42%; brain stem, 25%; pons, 10%; and corpus callosum, 3%. The decarboxylase activity in various mouse tissues was also determined as follows: liver, 403; brain, 145; kidney, 143; spinal cord, 59; lung, 21; and spleen, 10 pmol taurine formed/min/mg. No activity could be detected in skeleton muscle and heart, suggesting a different biosynthetic pathway for taurine synthesis in these tissues. The advantages and disadvantages of the new assay method are also discussed.

Effect of dietary taurine on blood pressure in spontaneously hypertensive rats

Previous studies have shown the dietary supplementation with sulfur amino acids modified the development of hypertension in rats. In the current study, it was found that the addition of taurine (3%) to the drinking water of rats during the period of 4–14 weeks of age had little effect on blood pressure in normotensive Wistar-Kyoto rats (WKR), and slightly retarded the development of hypertension in spontaneously hypertensive rats (SHR). In the stroke-prone substrain (SHR-SP), however, there is a highly significant reduction in the development of hypertension. The endogenous content of taurine in the liver of SHR-SP is less than 50 per cent of that measured in WKR. The livers of the SHR contain an intermediate amount of taurine. The cysteic acid decarboxylase activity of liver is similar in all three strains. The tissues of animals treated chronically with taurine contain only slightly greater amounts of taurine, with small but significant increases in brain taurine being noted. It appears that genetically hypertensive rats, particularly the SHR-SP substrain, have a defect in taurine metabolism, and that this may be related to the severity of hypertension. There is no evidence to suggest that taurine plays a normal regulatory role in blood pressure maintenance.

A sensitive radiometric assay for cysteic acid decarboxylase activity in crude enzyme preparations of rat liver and brain

1. 1. A method is described for the synthesis of l-[U- 14C]cysteic acid from l-[U- 14C]cysteine hydrochloride and for its subsequent utilisation as a substrate for cysteic acid decarboxylase activity in liver and brain. 2. 2. The enzyme determination relies on the entrapment of radio-labelled carbon dioxide in Hyamine hydroxide. 3. 3. The assay is sensitive, reliable and convenient and is particularly suitable for measuring the activity of the decarboxylase in crude enzyme preparations.

The synthesis of taurine from sulfate. IV. An alternate pathway for taurine synthesis by the rat.

SummaryThe rat is capable of synthesizing taurine from sulfate. The enzymatic pathway appears to be similar to that in chick liver which utilizes l-serine and activated sulfate (PAPS). The enzymes which catalyze this reaction sequence appear to be the same as those for the chick liver system, serine dehydrase, PAPS-sulfotransferase, and cysteic acid decarboxylase.

The synthesis of taurine from sulfate. 3. Further evidence for the enzymatic pathway in chick liver.

SummaryThe purpose of this research was to determine the enzymatic pathway for the synthesis of taurine from inorganic sulfate in chick liver. The enzymatically active proteins were obtained in the supernatant fraction from an ammonium sulfate precipitate (0.7 saturation) of chick liver homogenate using carboxymethylcellulose (CMC)-ion exchange chromatography. Experiments designed to ascertain the acceptor of the sulfate from 3′-phosphoadenosine-5′-phosphosulfate (PAPS) indicated that serine had the highest activity. Further, pyridoxal phosphate-dependent serine dehy-drase activity was required in the reaction utilizing serine to form taurine. The formation of taurine was preceded by the intermediate being converted to enzyme-bound cysteic acid. Inhibition studies indicated that PAPS-transferase, serine dehydrase, cysteic acid decarboxylase activities were required for this reaction, as well as a sulfhydryl requirement.

Formation and excretion of taurine in x-irradiated rats.

SummaryUrinary excretion profiles of taurine have been estimated in male Wistar rats exposed to doses of x-rays ranging from 100–1000 R. Maximum levels were observed in urine collected 24 hours after irradiation. Urinary taurine returned to normal values within 48 hours only in rats which had received sublethal doses (100–400 R). The high taurine levels persisted even after 72 hours in rats receiving more than LD50, i.e. 600–1000 R. The dose–response relationship obtained indicates a sort of a threshold dose beyond which the recovery mechanisms apparently do not operate.Urinary excess of taurine could be ascribed to enhanced liver cysteic acid decarboxylase activity. The increase in enzyme activity corresponds to the maximum appearance of taurine in the urine. Cysteine sulphinic acid decarboxylase did not show any variation.Formation of taurine in vivo was also followed up after intraperitoneal injection of cysteine-3-14C. There was enhanced recovery of radioactivity of the injected amino acid in blood and urine of x-irradiated animals, indicating increased synthesis of taurine. Hypertaurinuria could be prevented by prior treatment with desoxypyridoxine.

Observations on cysteic acid decarboxylase

Observations on cysteic acid decarboxylase