Sulfur compounds, metabolism

Divalent sulfur compounds are achiral, but trivalent sulfur compounds called sulfonium stilts (R3S+) can be chiral. Like phosphines, sulfonium salts undergo relatively slow inversion, so chiral sulfonium salts are configurationally stable and can be isolated. The best known example is the coenzyme 5-adenosylmethionine, the so-called biological methyl donor, which is involved in many metabolic pathways as a source of CH3 groups. (The S" in the name S-adenosylmethionine stands for sulfur and means that the adeno-syl group is attached to the sulfur atom of methionine.) The molecule has S stereochemistry at sulfur ana is configurationally stable for several days at room temperature. Jts R enantiomer is also known but has no biological activity. 

D. M. Greenberg (Ed.), Metabolic Pathways, 3rd ed., Vol. VII Metabolism of Sulfur Compounds, Academic Press, New York, 1975. 

FIGURE 11.9 Elimination reactions during metabolism of aliphatic sulfur compounds (a) cysteine, (b) methionine, and (c) 2-dimethylsulfoniopropionate. 

Metabolism of this thiosulfate or of other sulfur compounds... 

Among the bacteria that can inhabit an oil reservoir are the sulfur bacteria that use sulfur compounds in their metabolism. These bacteria produce hydrogen sulhde, which has been responsible for extensive corrosion in the oil field. Thus exclusion of these bacteria from MEOR is highly desirable. The net effect of souring a reservoir is a decrease in the economic value of the reservoir [1835]. 

The data reported identifies sulfur substrates tested for growth as sole sulfur source for the various strains. The strains may metabolize other sulfur compounds (not listed). A complete name of listed strains in Table 3 comprises Rhodococcus sp. SY1 Rhodococ-cus sp. H-2 Rhodococcus sp. D-l Rhodococcus ECRD-1 Gordona CYKS1 Nocar-dia sp. CYKS2 Paenibacillus All-2 Mycobacterium sp. WU-F1 Mycobacterium sp. WU-0103 Mycobacterium phlei sp. GTIS10 and Agrobacterium MC501. 

Kelly DP, ShergiU, JK, Wood AP. 1997. Oxidative metabolism of inorganic sulfur compounds by bacteria. Antonie Leeuwenhoek 71 95-107. 

In the context of the desirability of removing sulfur compounds from fuels, a bacterial strain has been identified that will metabolize thianthrene to water-soluble products under aerobic conditions (83MI5). A thermophilic organism, Sulfolobus acidocaldarius, removed 38% of the sulfur, as measured by sulfate release, in 4 weeks at 70°C (87MI2). 

There are only a few reports on the absorption, metabolism, and excretion of garlic s sulfur compounds available. Further, until now it is not known what metabolic form of allicin actually reaches the target cells, and it is still unknown how garlic compounds might function in the body. 

Brannan, D. K., and Caldwell, D. E. (1980). Thermothrix chiopara Growth and metabolism of a newly isolated thermophile capable of oxidizing sulfur and sulfur compounds. Appl. Environ. Microbiol. 40, 211-216. 

Cysteine not only is an essential constituent of proteins but also lies on the major route of incorporation of inorganic sulfur into organic compounds.443 Autotrophic organisms carry out the stepwise reduction of sulfate to sulfite and sulfide (H2S). These reduced sulfur compounds are the ones that are incorporated into organic substances. Animals make use of the organic sulfur compounds formed by the autotrophs and have an active oxidative metabolism by which the compounds can be decomposed and the sulfur reoxidized to sulfate. Several aspects of cysteine metabolism are summarized in Fig. 24-25. Some of the chemistry of inorganic sulfur metabolism has been discussed in earlier chapters. Sulfate is reduced to H2S by sulfate-reducing bacteria (Chapter 18). The initial step in assimilative sulfate reduction, used by... 

DU VIGNEAUD, VINCENT (1901-1978). An American biochemist who won the Nobel prize lor chemistry in 1955. His work involved Ihe study of the metabolism of biologically significant sulfur compounds, which led to the finding of transmethylation in mammalian metabolism. He isolated and proved the structure of Ihe vitamin biotin, and synthesized penicillin, oxytocin, and the vasopressin hormone of the posterior pituitary. His education was at Rochester. Yale. St. Louis, and George Washington Universities. 

In the chain from soils to plants to humans, inorganic sulfur, or more accurately, the sulfate ion (SO42-), is taken up by plants and converted within the plant to organic compounds (the sulfur amino acids). These amino acids combine with other amino acids to make up plant protein. When the plant is eaten by a human or by livestock animals, die protein is broken down and die amino acids are absorbed from the digestive tract and recombined 111 the proteins of the animal body. The most important feature of sulfur in die food chain is that plants use inorganic sulfur compounds to make sulfur amino acids, whereas animals and humans use the sulfur amino acids for their own processes and excrete inorganic sulfur compounds resulting from the metabolism of the sulfur amino acids. 

Free amino acids are further catabolized into several volatile flavor compounds. However, the pathways involved are not fully known. A detailed summary of the various studies on the role of the catabolism of amino acids in cheese flavor development was published by Curtin and McSweeney (2004). Two major pathways have been suggested (1) aminotransferase or lyase activity and (2) deamination or decarboxylation. Aminotransferase activity results in the formation of a-ketoacids and glutamic acid. The a-ketoacids are further degraded to flavor compounds such as hydroxy acids, aldehydes, and carboxylic acids. a-Ketoacids from methionine, branched-chain amino acids (leucine, isoleucine, and valine), or aromatic amino acids (phenylalanine, tyrosine, and tryptophan) serve as the precursors to volatile flavor compounds (Yvon and Rijnen, 2001). Volatile sulfur compounds are primarily formed from methionine. Methanethiol, which at low concentrations, contributes to the characteristic flavor of Cheddar cheese, is formed from the catabolism of methionine (Curtin and McSweeney, 2004 Weimer et al., 1999). Furthermore, bacterial lyases also metabolize methionine to a-ketobutyrate, methanethiol, and ammonia (Tanaka et al., 1985). On catabolism by aminotransferase, aromatic amino acids yield volatile flavor compounds such as benzalde-hyde, phenylacetate, phenylethanol, phenyllactate, etc. Deamination reactions also result in a-ketoacids and ammonia, which add to the flavor of... 

Sulfur compounds produced by yeast metabolism (and residues of pesticide treatment)... 

Hydrolytic enzymes can also catalyzed the esterification of alcohols or acids with hetero atoms.1617 Some examples for the reactions of phosphorous and sulfur compounds by lipases are shown in Figure 16. By the repeated enantioselective acylation and hydrolysis of a hydroxyl phosphonate and its acetate with lipase AH, phosphonic acid analogue of carnitine (essential cofactor of fatty acid metabolism), (A)-phosphocarniiine, and its enantiomer were synthesized as shown in Figure 16 (b). 

Emissions of biogenic sulfur compounds to the atmosphere result from an imbalance between metabolic formation processes and biological or physicochemical consumption processes, determined on the spatial scale of the available methods for measuring emission fluxes. Variability in emissions... 

The anaerobic metabolism of acrylate and 3-mercaptopropionate (3-MPA) was studied in slurries of coastal marine sediments. The rate of these compounds is important because they are derived from the algal osmolyte dimethylsulfoniopropionate (DMSP), which is a major organic sulfur compound in marine environments. Micromolar levels of acrylate were fermented rapidly in the slurries to a mixture of acetate and propionate (1 2 molar ratio). Sulfate-reducing bacteria subsequently removed the acetate and propionate. 3-MPA has only recently been detected in natural environments. In our experiments 3-MPA was formed by chemical addition of sulfide to aciylate and was then consumed by biological processes. 3-MPA is a known inhibitor of fatty acid oxidation in mammalian systems. In accord with this fact, high concentrations of 3-MPA caused acetate to accumulate in sediment slurries. At lower concentrations, however, 3-MPA was metabolized by anaerobic bacteria. We conclude that the degradation of DMSP may ultimately lead to the production of substrates which are readily metabolized by microbes in the sediments. 

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