Sulphur metabolism

C. H. Rothera. Experiments on Cystin and its Relation to Sulphur Metabolism. J. 

In addition to the amino acids found in proteins, the cell also contains a number of other aminp acids that are not normally found in peptides. This includes ornithine, unimportant intermediate in the urea cycle, selenocysteine, a very rare component of some proteins and homocysteine, an important intermediate in sulphur metabolism. 

What Canfield and Teske propose, then, is that modern types of ecosystems, requiring modern levels of oxygen, began to develop soon after the end of the last snowball Earth. They back their conclusions by molecular-clock calculations, which confirm an increase in the number of species of sulphur-metabolizing bacteria at this time. Thus, Canfield and Teske project a rise in atmospheric oxygen to nearly modern levels in the final years of the Precambrian. 

Rey, D.A., Nentwich, S.S., Koch, D.J., Riickert, C., Piihler, A., Tauch, A., and Kalinowski, J. (2005) The McbR repressor modulated by the effector substance S-adenosylhomocysteine controls directly the transcription of a regu-lon involved in sulphur metabolism... 

SurR a transcriptional activator and repressor controlling hydrogen and elemental sulphur metabolism in Pyro-coccus furiosus. Mol. Microbiol., 71,... 

Cysteine formation through the addition of thiosulphate to serine or O-acetyl serine may play a role in the sulphur metabolism of some organisms. The reactions involved are similar in form to those described above, with S-sulphocysteine serving an intermediary role. Since thiosulphate is not generally considered to be on the main line of inorganic sulphur metabolism this probably represents an adaptation to certain special environments. 

This is a heriditary disorder of sulphur metabolism in which sulphite, thiosulphate and S-sulphocysteine occur in increased amounts in the urine. Affected individuals can have dislocated lenses together with a sudden onset of paresis, and death at an early age results. 

Therefore, it could be concluded that, the essentiality of Se for higher plants is still unproven, but Se is considered a beneficial nutrient for many plant species. This review focuses on the biochemical responses of plants to Se, the assimilation of Se in plants and possible incorporation into proteins. Molecular approaches to understanding Se toxicity and tolerance have increased the knowledge of mechanisms of action, and the molecular biology of Se in transgenic plants is detailed with special reference to the similarity with sulphur metabolism, S/Se transporters and important assimilation enzymes. 

Hawkesford MJ, De Kok LJ (2006) Managing sulphur metabolism in plants. Plant Cell Environ... 

Speculation has ascribed several functions to salivary thiocyanate a) an oral antiseptic, (6) an activator of ptyalin, (c) a form in which —CN compounds are eliminated, [d) a by-product of sulphur metabolism, possibly related to the taurine of bile. 

Formaldehyde, sulphur dioxide and glutaraldehyde react with amino groups. If these groups are essential for metabolic activity, cell death will follow reactions of this nature. Chlorinated fso-thiazolones as well as acting on -SH groups, (Section 3.4), can react with -NH2 groups. 

Suylen GMH, PJ Large, JP van Dijken, JG Kuenen (1987) Methyl mercaptan oxidase, a key enzyme in the metabolism of methylated sulphur compounds by Hyphomicrobium EG. J Gen Microbiol 133 2989-2997. 

The carcinogenic and mutagenic effects of 1,2-dibromoethane is due to its ability to bind to DNA and RNA with metabolic activation. The mechanism of action for the antispermatogenic effects is probably related to the removal of sulphur from cysteine in the nucleus of the spermatozoa. Clinical intervention to interfere with these mechanisms has yet to be developed. 

The metabolism of sulphur plays an important role in metal response, since most chelators, including metallothioneins and phytochelatins, contain this element. APSl encodes an ATP sulfurylase and Brassica juncea has been engineered to constitutively express this gene (Pilon-Smits et al., 1999). The plants showed increased S assimilation, higher glutathione (GSH) levels and were more tolerant to Se, accumulating 2-fold higher Se levels in the shoots. 

Trudinger PA. 1967. The metabolism of inorganic sulphur compounds by thiobacilli. Rev Pure Appl Chem 17 1-24. 

The pharmacokinetics of amezinium metilsulphate in man have been reported [413-415]. The first step of metabolism consists in demethylation affording the pharmacologically inactive, uncharged 5-amino-2-phenyl-3(2//)-pyridazinone hydroxylated pyridazinones and sulphuric acid conjugates thereof have been isolated [413],... 

Ferredoxins (Fds) are widespread in the three domains of life and an abundance of sequence data and structural information are available for Fds isolated from several sources. In particular, the bacterial type Fds are small electron-transfer proteins that posses cubane xFe-yS clusters attached to the protein matrix by Fe ligation of Cys via a conserved consensus ligating sequence. The archaeal type ferredoxins are water-soluble electron acceptors for the acyl-coenzyme A forming 2-oxoacid/ferredoxin oxidoreductase, a key enzyme involved in the central archaeal metabolic pathways. Fds have been distinguished according to the number of iron and inorganic sulphur atoms, 2Fe-2S, 4Fe-4S/3Fe-4S (Fig. Ib-d) and Zn-containing Fds. 

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