Cysteine sulphinate

The same group have used the enzyme combination employed in the aspartate deracemization cited above to deracemize 2-naphthylalanine, hut have made use of an interesting innovation introduced by Helaine et al to pull over the poised equilibrium of the transamination reaction. Cysteine sulphinic acid was used as the amino donor in the transamination. The oxoacid product spontaneously decomposes in to pyruvic acid and SO2 (Scheme 3). 

Universal thiol precursor (X—SH) of oxidation products Cysteine sulphinic acid (X—SCFH), Cysteic acid (X-SO-jH) Cystine (X-S-S-X) ... 

L-Aspartic Acid L-Cysteic Acid L-Cysteine Sulphinic Acid L-Glutamic Acid... 

Taurine - A glyclne-like, sulphur containing amino acid, taurine (12) is found in reasonably high concentrations throughout the mammalian central nervous system and in heart.In brain, taurine is formed as a result of the decarboxylation of cysteine sulphinic acid (15) to hypotau-rlne (8 ), which in turn is oxidized to form taurine.Like other transmitter candidates, taurine is accumulated and released by brain tissue and the accumulation can be inhibited by ouabain. Clinically, significant alterations in taurine levels may be associated with retinitis pigmentosa, epilepsy, mongolism, and possibly heart disease. 

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. 

It has been mentioned above that there are few naturally occurring sulphonic acids. One notable exception is taurine (6), which is formed biosynthetically in several steps. One of these steps involves the oxidation of either cysteine sulphinic acid or hypotaurine (both of which contain a sulphinic acid group) to sulphonic acids. This reaction is, of course,... 

Enzymatic decarboxylation169 of L-cysteic acid-35S (equation 86) by the tissues of chicken embryo has been investigated by Fromageot and coworkers170. Enzyme preparations from liver appeared to be the most active, and the authors determined [35S]taurine as well as unreacted 35S-cysteic acid, 35S-/Lsulphonylpyruvic acid and 35S-sulphate. The reaction is inhibited by L-cysteine sulphinic acid, by DL-a-methylcysteic acid, CH2ICOONa, NaCN and by hydroxylamine. The enzyme is activated by pyridoxal phosphate. 

The more complex sulphur requirements of the marine animals are met largely by cysteine, cystine, methionine, biotin, and thiamine (Young and Maw, 1958) (Fig. 4). Cysteine is a component of the tripeptide glutathione and a precursor of taurine. Methionine is as an essential amino acid involved in biosynthesis of proteins, creatine and adrenaline. Adenosylmethionine is considered to be the active part in transmethylation, e.g. of choline. Methionine is part of the pathways to homocysteine, cystathionine and methylthioadenosine (Young and Maw, 1958). Various organisms convert cysteine and/or cystine into mercapturic acids, cysteine sulphinic acid, and thiazolidine derivatives (Zobell, 1963). 

Glutamate Cysteine sulphinate Cysteate Glutamate y-Methylene-glutamate Histidine... 

Wu J.-Y. (1982) Purification and characterization of cysteic/cysteine sulphinic acids decarboxylase and L-glutamate decarboxylase in bovine brain. Proc Natl Acad. Set. USA 79, 4270-4274. 

The only thiol oxidation reaction to oxy-derivatives of general biochemical significance is that of cysteine to alanine 3-sulphinic acid (cysteine sulphinic add) . This is thought to be the initial reaction in the... 

Cysteine-sulphinic add, by transamination, can yield j3-sulphinyl-pyruvic add which is decomposed into pyruvic acid and SO,— which... 

Hope, D.B., 1955, Pyridoxal phosphate as the coenzyme of the mammalian decarboxylase for L-cysteine sulphinic and L-cysteic acids, Biochem. J., 59 497-500. 

J.G. Jacobsen and L.H. Smith, Jr., Comparison of decarboxylation of cysteine sulphinic acid-l-C and cysteic acid-l-C by hximan, dog and rat liver and brain. 

S.S. Oja, M.L. Karvonen and P. Lahdesmaki, Biosynthesis of Taurine and Enhancement of Decarboxylation of Cysteine Sulphinate and Glutamate by the Electrical Stimulation of Rat Brain Slices, Brain. Res. 55 173 (1973). 

The oxidation rate was also dependent on the concentration of hypotaurine in the incubation medium. The reaction appeared to obey simple Michaelis-Menten kinetics (Fig. 2). The kinetic constants were estimated from a linear transformation of the Michaelis-Menten equation in a t against v/s plot. The apparent Michaelis constant ( ) was about 0.2 ramol/1 and the maximal velocity (F) about 0.1 ymol/s X kg. In our crude liver homogenate the apparent for hypotaurine oxidation was of the same order of magnitude as for the partially purified L-cysteine sulphinate decarboxylase (Jacobsen et al., 1964), the preceding enz3nne in the biosynthesis pathway. 

Oja, S. S., Karvonen, M.-L., and Lahdesmaki, P., 1973, Biosynthesis of taurine and enhancement of decarboxylation of cysteine sulphinate and glutamate by the electrical stimulation of rat brain slices. Brain Res., 55 173. 

In a previous work we have demonstrated that cysteine Is oxidized to cysteine sulphinate by cysteine dIoxygenase In rat retina (46). In the retina the final reaction product Is almost exclusively cysteine sulphinate, but In brain a considerable portion of It Is further oxidized to cysteate (47). 

Cysteine sulphinate decarboxylase activity has been detected In retina of several species (48, 49), In chick retina this enzymatic activity was found associated with the crude nuclear fraction for approximately 18% and with the crude mitochondrial fraction for about 27% whereas about 55% was found in the soluble fraction (49) ... 

Cysteine dioxygenase activity was assayed in presence of only cysteine or with cysteine, Fe"" and NAD". in all the primary and secondary subcellular fractions Fe" and NAD were able to increase the cysteine sulphinate production (Table III).This activating effect was different in the various subcellular fractions studied, the maximum being obtained in the soluble and synaptosomal fractions and the lowest in the nuclear and purified mitochondrial fractions. 

This activity is mainly located in particulate components of the primary subcellular fractions. About 35% of the enzyme activity is present in the crude mitochondrial fraction.Further subfractionation has shown that half of the cysteine sulphinate decarboxylase activity, present in this fraction, is localized In synaptosomes... 

Cysteine sulphinate and cysteate are obviously decarboxylated by the same enzyme,The ratio between the decarboxylation of cysteine sulphinate and of cysteate was constant throughout all the steps of our fractionation procedure.This ratio is approx. 6.6 and is similar to that reported In rat liver (56). 

The discovery of the decarboxylation of cysteine sulphinate to hypotaurine, which Is then oxidized to taurine, led to the proposition that this pathway represents the main biosynthetic route for taurine in animal tissues (57, 58). The finding of consistent amounts of hypotaurine in organs and body fluids after injection or feeding... 

Table IV, Cysteine sulphinate decarboxylase activity in primary and secondary subcellular fractions from ox retina...

Values are the mean of 15 experiments + SEM,Cysteine sulphinate decarboxylase activity was assayed according toMacaione et al,(48) ... 

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