Reaction products from Clostridium

Commercial A -acetylneuraminic acid aldolase from Clostridium perfringens (NeuAcA EC 4.1.3.3) catalyzes the addition of pyruvate to A-acetyl-D-mannosamine. A number of sialic acid related carbohydrates are obtained with the natural substrate22"24 or via replacement by aldose derivatives containing modifications at positions C-2, -4, or -6 (Table 4)22,23,25 26. Generally, a high level of asymmetric induction is retained, with the exception of D-arabinose (epimeric at C-3) where stereorandom product formation occurs 25 2t The unfavorable equilibrium constant requires that the reaction must be driven forward by using an excess of one of the components in order to achieve satisfactory conversion (preferably 7-10 equivalents of pyruvate, for economic reasons). 

Table IL Reaction Products of AmylopuUulanase from Clostridium thermohydrosulfuricum Strain 39E on High MW Polysaccharides ...

Further differentiation was obtained using the chromophoric cel-looligodextrins and a rapid and sensitive HPLC analysis of the reaction products (1). Specific degradation patterns were obtained for several enzymes such as those from Clostridium cloned in E. coli (Fig. 2). 

Bechamp (15) in 1867 was the first to describe methane production from a simple fermentation product, ethanol, and to attribute it to a microbial fermentation. The second product he found to be formed from ethanol was caproate, now known to be produced by Clostridium kluyveri (4). Thus, carbon-carbon bonds are not only destroyed early in the fermentation chain, they can also be reductively synthesized if the reaction is paired with the energy yielding oxidation of another substrate (c/. initial fermentations of acetate and ethanol and also of H2, Figure 1). Several successive fermentations may then be required to convert these products to methane and CO2. 

For example78. (2 )-2-methyI-3-phenylpropanate can be prepared in the described manner in 95 % yield using the enoate reductase from Clostridium LAI. Immobilization of the enzyme 7 gives no improvement in the reaction rates in fact, when free or immobilized cells are used the reaction becomes slower. A part of the current is used for hydrogen production. 

A preparation (Wright and Anderson, 1958) from Clostridium sticklandii catalyzed the reaction PGA + pyruvate + CoA — acetyl CoA + FH2. Since the diglutamyl and triglutamyl pterins and their J T -formyl derivatives were reduced, such a reductase system can account for the transformation of exogenous PGA into the reduced coenzymatic products. An enzyme from Micrococcus lactilyticus formed FH2 the reaction required an electron donor such as pyruvate or a-ketobutyrate, a dithiol such as dimer-captopropanol, orthophosphate, and reduced CoA. This enzyme did not form FH4 derivatives. 

The activities of intracellular enzymes give an indication of the activity of certain metabolic pathways. They are classically assayed by performing their specific reactions in vitro, using the conversion of natural or artificial substrates and often some additional detection reaction. The sample preparation procedure involves cell harvesting and preparation of cell extracts. A well-studied example is the metabolic shift in Clostridium acetobutylicum from acid to solvent production, the so-called solvent shift. Andersch et al. [48] studied the activities of 10 different enzymes involved in this shift, in batch cultivations where the shift is self-induced by the products formed, and under continuous culture conditions with an externally induced shift. 

Sodinm nitrite is commonly utilized in food preservation. In spite of its known potential for metabolism to carcinogenic nitrosamines, nitrite snpplementation is still in widespread nse in nntrition because the addition of nitrite (plus a reducing agent such as ascorbate) has two desirable effects it imparts a red color to meats (primarily a result of the production of nitrosylheme from myoglobin ) and, perhaps more importantly, the organism responsible for botulism Clostridium botulinum) is exquisitely sensitive to this treatment. There is indeed a massive literature on the role of NO and its reactions in foods in the nutrition fields and is worthy of scrutiny by researchers in the biological effects of endogenously produced -NO in mammahan systems. 

There is yet another biochanical reaction involving CO (apart from its role as a transmitter substance in animals) which should be addressed here CO is activated and linked to some Ni-CH moiety in a [Ni(deprotonated ohgopeptide)(CH3)] complex attached to a Ni or Cu car-bonylpolythiolate complex which affords acetyl-CoA via some Ni acetyl system by CO shift and insertion in a manner very similar to the Monsanto process for production of acetic add from CO and methanol. The latter affords methyl groups attached to the metal (Ni here, Ru in the original Monsanto process). This transformation takes place in a Clostridium, namely Moorella thermoacetica. 

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