Escherichia coli substrates

Polyunsaturated fatty acids pose a slightly more complicated situation for the cell. Consider, for example, the case of linoleic acid shown in Figure 24.24. As with oleic acid, /3-oxidation proceeds through three cycles, and enoyl-CoA isomerase converts the cA-A double bond to a trans-b double bond to permit one more round of /3-oxidation. What results this time, however, is a cA-A enoyl-CoA, which is converted normally by acyl-CoA dehydrogenase to a trans-b, cis-b species. This, however, is a poor substrate for the enoyl-CoA hydratase. This problem is solved by 2,4-dienoyl-CoA reductase, the product of which depends on the organism. The mammalian form of this enzyme produces a trans-b enoyl product, as shown in Figure 24.24, which can be converted by an enoyl-CoA isomerase to the trans-b enoyl-CoA, which can then proceed normally through the /3-oxidation pathway. Escherichia coli possesses a... 

Gentamidns C, Ci and Ci. Acylation 3-/V-Acetyl derivatives of the respective substrates Escherichia coli Klebsiella penumoniae Pseudomonas aeruginosa... 

Neamine Neomydn Ribostamydn Gentamicins A, B, Cia. c2 Kanamydn B Sisomidn Tobramydn Dihydrostreptomydn Pseudomonas aeruginosa Escherichia coli Pseudomonas aeruginosa Escherichia coli Staphylococcus aureus 3 -0-Phosphorylated Pseudomonas aeruginosa derivatives of the respective substrates ... 

Enzyme preparations from liver or microbial sources were reported to show rather high substrate specificity [76] for the natural phosphorylated acceptor d-(18) but, at much reduced reaction rates, offer a rather broad substrate tolerance for polar, short-chain aldehydes [77-79]. Simple aliphatic or aromatic aldehydes are not converted. Therefore, the aldolase from Escherichia coli has been mutated for improved acceptance of nonphosphorylated and enantiomeric substrates toward facilitated enzymatic syntheses ofboth d- and t-sugars [80,81]. High stereoselectivity of the wild-type enzyme has been utilized in the preparation of compounds (23) / (24) and in a two-step enzymatic synthesis of (22), the N-terminal amino acid portion of nikkomycin antibiotics (Figure 10.12) [82]. 

Similarly, Ikehara, Tazawa, and Fukui (51) have found that the nucleotides 8-bromo and 8-oxoadenosine 5 -diphosphate, 8-bromo-, 8-oxo, and 8-dimethylaminoguanosine 5 -diphosphate are all inactive as substrates for homopolymer synthesis catalyzed by polynucleotide phosphorylase from Escherichia coli. Some of the results were later confirmed by Kapuler, Monny, and Michelson (52), who found that neither 8-bromo- nor 8-oxoguanosine 5 -diphosphate was active as a substrate for homopolymerization with polynucleotide phosphorylases isolated both irom Azotobacter vinelandii and . coli. 

Recently, a potential cytosolic component of the MEP precursor pathway, xylulose kinase, has been cloned and tested for function in an Escherichia coli complementation system. " The kinase activates exogenous xylulose in the cytoplasm. DXP is the precursor for DXS, which resides in the plastid, suggesting the activated substrate must be transported into the plastid. Another xylulose kinase homologue in Arabidopsis that contains a plastid targeting sequence was not active in the E. coli system, suggesting that it may have some other function in the plastid. Perhaps plant and bacterial tissue cultures may be fed xylulose to condition accumulation of isoprenoid metabolites. 

Until 1987, the (R)-PaHNL from almonds was the only HNL used as catalyst in the enantioselective preparation of cyanohydrins. Therefore, it was of great interest to get access to HNLs which catalyze the formation of (5 )-cyanohydrins. (5 )-SbHNL [EC 4.1.2.11], isolated from Sorghum bicolor, was the first HNL used for the preparation of (5 )-cyanohydrins. Since the substrate range of SbHNL is limited to aromatic and heteroaromatic aldehydes as substrates, other enzymes with (5 )-cyanoglycosides have been investigated as catalysts for the synthesis of (5 )-cyanohydrins. The (5 )-HNLs from cassava (Manihot esculenta, MeHNL) and from Hevea brasiliensis (HbHNL) proved to be highly promising candidates for the preparation of (5 )-cyanohydrins. Both MeHNL and HbHNL have been overexpressed successfully in Escherichia coli, Saccharomyces cerevisiae and Pichia pastoris. 

In bacteria, accumulation of substrates against a concentration gradient can occur through two main classes of transport systems (see [30] for a summary). The prototype of the first class of transporters is the /3-galactoside permease of Escherichia coli (see [31]). It is a relatively simple system involving only a single membrane-bound protein. It catalyzes a lactose-H symport. Other transporters... 

Prieto MA, A Perez-Aranda, JL Garcia (1993) Characterization of an Escherichia coli aromatic hydroxylase with a broad substrate range. J Bacteriol 175 2162-2167. 

The conditions under which these function and their regulation depend on the organism. For example, in Escherichia coli, oxygen represses the synthesis of the other reductases, and under anaerobic conditions the reductases for fumarate, DMSO, and TMAO are repressed by nitrate. This does not apply to Wolinella succinogenes in which sulfur represses the synthesis of the more positive electron acceptors nitrate and fumarate (Lorenzen et al. 1993). The DMSO reductase from Escherichia coli (Weiner et al. 1988) has a broad substrate versatility, and is able to reduce a range of sulfoxides and A-oxides. Anaerobic sulfate reduction is not discussed here in detail. 

Wan J, TK Tokunaga, E Brodie, Z Wang, Z Zheng, D Herman, TC Hazen, MK Firestone, SR Sutton (2005) Reoxidation of bioreduced uranium under reducing conditions. Environ Sci Technol 39 6162-6169. Weiner JH, DP Macisaac, RE Bishop, PT Bilous (1988) Purification and properties of Escherichia coli dimethyl sulfoxide reductase, an iron-sulfur molybdoenzyme with broad substrate specificity J Bacterial 170 1505-1510. 

The degradation of phenylacetate has remained enigmatic for several years, and details of the pathway used by Escherichia coli were elucidated using C-labeled substrate. Using the full complement of NMR technology, the structures of critical intermediates were determined and provided details of an unusual pathway (Ismail et al. 2003). 

Nucleotide pools and transmembrane potential in bacteria after exposure to penta-chlorophenol were investigated using P NMR. Differences were used to differentiate Escherichia coli, which does not degrade this substrate and a Flavobacterium sp., which is able to do so (Steiert et al. 1988). 

Bej, A. K. McCarty, S. C. Atlas, R. M. Detection of coliform bacteria and Escherichia coli by multiplex polymerase chain reaction comparison with defined substrate and plating methods for water quality monitoring. Appl. Environ. Microbiol. 1991, 57, 2429-2432. 

A thermally stable NHase from Comamonas testosteroni 5-MGAM-4D (ATCC 55 744) [22] was recombinantly expressed in Escherichia coli, and the resulting transformant cells immobilized in alginate beads that were subsequently chemically cross-linked with glutaraldehyde and polyethylenimine. This immobilized cell catalyst (at 0.5 % dew per reaction volume) was added to an aqueous reaction mixture containing 32wt% 3-cyanopyridine at 25 °C, and a quantitative conversion to nicotinamide was obtained. The versatility of this catalyst system was further illustrated by a systematic study of substrates, which included... 

A recombinant Escherichia coli strain containing the cloned limonene hydratase gene was able to grow in a water-limonene two-phase system and converted limonene to a-terpineol [36], Limonene, a cost-effective and readily available monoterpene, served both as the substrate and the neat solvent for the production of a-terpineol. 

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