Clostridium Activation

Selenocysteine was identified in 1976 (57) in a protein produced by Clostridium stricklandii, and it is thought to be the form in which selenium is incorporated, stoichiometricaHy, into proteins. Studies with rats show that over 80% of the dietary selenium given them is incorporated into proteins, thus selenocysteine takes on metaboHc importance. Selenoproteins having known enzymatic activities contain selenocysteine at the active sites. Two other forms of metabohc selenium are recognized methylated selenium compounds are synthesized for excretion, and selenium is incorporated into some transfer ribonucleic acids (tRNAs) in cultured cells (58). Some of the more important seleno-compounds are Hsted in Table 4. Examples of simple ring compounds are shown in Eigure 4. 

The most ingenious exocytosis toxins, however, come from the anaerobic bacteria Clostridium botulinum and Clostridium tetani. The former produces the seven botulinum neurotoxins (BoNTs) A-G the latter produces tetanus neurotoxin (TeNT). All eight toxins consist of a heavy (H) chain and a light (L) chain that are associated by an interchain S-S bond. The L-chains enter the cytosol of axon terminals. Importantly, BoNT L-chains mainly enter peripheral cholinergic terminals, whereas the TeNT L-chain mainly enters cerebral and spinal cord GABAergic and glycinergic terminals. The L-chains are the active domains of the toxins. They are zinc-endopeptidases and specifically split the three core proteins of exocytosis, i.e. the SNAREs (Fig. 1 inset). Each ofthe eight toxins splits a... 

Tetanus is a disease caused by the release of neurotoxins from the anaerobic, spore-forming rod Clostridium tetani. The clostridial protein, tetanus toxin, possesses a protease activity which selectively degrades the pre-synaptic vesicle protein synaptobrevin, resulting in a block of glycine and y-aminobutyric acid (GABA) release from presynaptic terminals. Consistent with the loss of neurogenic motor inhibition, symptoms of tetanus include muscular rigidity and hyperreflexia. The clinical course is characterized by increased muscle tone and spasms, which first affect the masseter muscle and the muscles of the throat, neck and shoulders. Death occurs by respiratory failure or heart failure. 

Lecithinase is produced by Clostridium perfringens. This is a calcium-dependent lecithinase whose activity depends on the ability to split lecithin. Since lecithin is present in the membrane of many different kinds of cells, damage can occur throughout the body. Lecithinase causes the hydrolysis of erythrocytes and the necrosis of other tissue cells. 

Zhang et al. isolated Clostridium hydroxybenzoicum containing two inducible 4-hydroxybenzoate decarboxylase and 3,4-dihydroxybenzoate decarboxylase that form phenol and catechol (1,2-dihydroxybenzene), respectively. The organism does not further metabolize phenol and catechol produced by these reactions. The carboxylation activities of the two purified decarboxylases are not... 

Wells JE, PB Hylemon (2000) Identification and characterization of a bile acid 7a-dehydroxylation operon in Clostridium sp. strain TO-931, a highly active 7a-dehydroxylating strain isolated from human feces. Appl Environ Microbiol 66 1107-1113. 

Wagner R, JR Andreesen (1979) Selenium requirement for active xanthine dehydrgenase from Clostridium acidiurici and Clostridium cylindrosporum. Arch Microbiol 121 255-260. 

Gladyshev VN, SV Khangulov, TC Stadtmann (1994) Nicotinic acid hydrolase from Clostridium barkeri electron paramagnetic studies show that selenium is coordinated with molybdenum in the catalytically active selenium-dependent enzyme. Proc Natl Acad USA 91 232-236. 

Fraisse L, H Simon (1988) Observations on the reduction of non-activated carboxylates by Clostridium formicoaceticum with carbon monoxide or formate and the influence of various viologens. Arch Microbiol 150 381-386. 

Reduction of nitroarenes has been demonstrated in species of Clostridium and Eubacte-rium, and was associated with the reduction in the mutagenic activity of 1-nitropyrene, and... 

Stadtman 1971 Kung et al. 1971). Degradation is initiated by hydroxylation of the ring, and the level of nicotinic acid hydroxylase is snbstantially increased by the addition of selenite to the medinm (Imhoff and Andreesen 1979). Nicotinate hydroxylase from Clostridium barkeri contains molybdenum that is coordinated to seleninm, which is essential for hydroxylase activity (Gladyshev et al. 1994). The most remarkable featnre of the pathway is the mechanism whereby 2-methylene-glntarate is converted into methylitaconate by a coenzyme Bi2-mediated reaction (Knng and Stadtman 1971). 

Although it had been assumed that only hypoxanthine dehydrogenase is required for the conversion of hypoxanthine (6-hydroxypurine) into uric acid, in Clostridium purinolyti-cum, two enzymes, both of which contain a selenium cofactor, are required. The enzymes differ in the molecular mass of their subunits, in their terminal amino acid sequences, in their kinetic parameters, and in their specific activities for purines (Self and Stadman 2000). Purine hydroxylase converts purine into hypoxanthine and xanthine (2,6-dihy-droxypurine), which is then further hydroxylated to uric acid (2,6,8-trihydroxypurine) by xanthine dehydrogenase (Self 2002). 

Imhoff D, JR Andreesen (1979) Nicotinic acid hydroxylase from Clostridium barkeri selenium-dependent formation of active enzyme. FEMS Microbiol Lett 5 155-158. 

Similar to catechins, several studies have reported that proanthocyanidins exhibit a more or less pronoimced antibacterial activity. Chimg et al. [76] reported that proanthocyanidins determine the growth inhibition of strains of Aeromonas spp.. Bacillus spp., Clostridium botulinum, Clostridium per-fringens, Enterobacter spp., Klebsiella spp., Proteus spp.. Pseudomonas spp.. Shigella spp., S. aureus. Streptococcus spp., and Vibrio spp. 

Various bacterial species have proven useful in MEOR. The principle is based on the species biochemical byproducts produced, such as gases, surfactants, solvents, acids, swelling agents, and cosurfactants, which facilitate the displacement of oil. In field experiments, in situ fermentation is often desirable for producing a great quantity of gases. Clostridium hydrosulfuricum 39E was found to have surface-active properties during simulated enhanced oil recovery experiments [1874]. 

It has been postulated that Chlamydia may produce a heat shock protein that causes tissue damage through a delayed hypersensitivity reaction. C. trachomatis may also possess DNA evidence of toxin-like genes that code for high-molecular-weight proteins with structures similar to Clostridium difficile cytotoxins, enabling inhibition of immune activation. This may explain the observation of a chronic C. trachomatis infection in subclinical PID. 

Altered release. Tetanus is an infectious disease caused by the bacterium Clostridium tetani. This bacterium produces a neurotoxin active on inhibitory synapses in the spinal cord. Motor neurons, which supply skeletal muscle and cause contraction, have cell bodies that lie in the spinal cord. Under normal circumstances, these motor neurons receive excitatory and inhibitory inputs from various sources. The balance of these inputs results in the appropriate degree of muscle tone or muscle contraction. Tetanus toxin prevents the release of gamma amino butyric acid (GABA), an important neurotransmitter active at these inhibitory synapses. Eliminating inhibitory inputs results in unchecked or unmodulated excitatory input to the motor neurons. The resulting uncontrolled muscle spasms initially occur in the muscles of the jaw, giving rise to the expression lockjaw. The muscle spasms eventually... 

Murashima, K., Chen, C.-L., Kosugi, A. et al. (2002) Heterologous production of Clostridium cellulovorans engB, using protease-deficient Bacillus subtilis, and preparation of active recombinant cellulosomes. Journal of Bacteriology, 184 (1), 76-81. 

Enoate reductase reduces a,/3-unsaturated carboxylate ions in an NADPH-dependent reaction to saturated carboxylated anions. Useful chiral synthons can be conveniently prepared by the asymmetric reduction of a triply substituted C—C bond by the action of enoate reductase, when the double bond is activated with strongly polarizing groups [22]. Enoate reductases are not commercially available as isolated enzymes therefore, microorganisms such as baker s yeast or Clostridium sp. containing enoate reductase are used to carry out the reduction reaction. 

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