Escherichia coli enzyme activity

The archetype Fe(II)/aKG hydroxylase is taurine/ q KG dioxygenase (TauD), an Escherichia coli enzyme that catalyzes the conversion of taurine (2-aminoethanesulfonic acid) to sulfite and aminoacetaldehyde, as illustrated in Scheme 1. TauD catalyzes the hydroxylation of a C H bond on the carbon adjacent to the sulfonate group of taurine. The product of this reaction then decomposes to yield hydrogen sulfite, which serves as an important source of sulfur for many microorganisms. A catalytic mechanism that has been proposed for these enzymes is provided as Scheme 2. Prior to the activation and hydroxylation of the Ci carbon on taurine, q KG binds to the Fe(II) center as a chelate, displacing two of the coordinated waters. Taurine then binds to the enzyme in the vicinity of the Fe(II) center, displacing the remaining water. 

PEPCs from enterobacteria such as Salmonella typhimurium and Escherichia coli are activated by acetyl CoA and inhibited by aspartate. Some properties of the enzyme from Rhodopseudomonas sp. No.7 were similar to those of the enterobacteria. However, the strain No.7 enzyme was different from enzymes of the enterobacteria in important points of metabolic regulation. It have been reported that the enzyme activities of the enterobacteria were increased by FBP and GTP. In contrast with this, the activity of the No.7 enzyme was not affected by FBP and reversibly inhibited by GTP and ATP (ADP). This differences may signify roles of the enzyme of strain No.7 related to the ethanol-assimilation and the enzymes of the enterobacteria to the glucose-assimilation in their own way. 

Smith, A.T. Santama, N. Dacey, S. Edwards, M. Bray, R.C. Thorneley, R.N.F. Burke, J.F. Expression of a synthetic gene for horseradish peroxidase C in Escherichia coli and activation of the recombinant enzyme with Ca and heme. J. Biol. Chem. 1990, 265, 13335-13343. 

Aldose-1-epimerase), quite widespread in animal tissue and bacteria, which catalyses mutarotation. The Escherichia coli enzyme has a maximum activity close to neutral pH. The activation energy 4G =11.9 kcal mol" is greatly lowered, as usual with respect to that of the non-enzymically catalysed reaction, close to 17 kcal mol". o-Glucose, D-galactose, and D-fucose are substrates but not D-mannose (Hucho and Wallenfels 1971). 

The X-ray structure of the transferase MurA from Enterobacter cloacae highly homologous to the Escherichia coli enzyme, is of a two-domain enzyme in an open conformation it was reasonably surmised that when the positive charges of an arginine and a lysine, whose repulsion were keeping the protein in the open conformation, were neutralised by the binding of UDPGlcNAc, the active site would close and eliminate water. 

In 1953, in the cell-free extract of a o-arabinose-adapted strain of Escherichia coli, enzymatic activity was found which converted o-arabinose (13) into d-eryt/zro-pentulose (o-ribulose, 14) [8]. Moreover, this enzyme was able to convert L-fucose (6-deoxy-L-galactose, 15) into the corresponding ketose 16 189]. In-depth investigations by the same authors confirmed this finding and revealed that the equilibrium could be shifted from originally 11% of L-fuculose (16) to over 80% by in situ complexation of the ketose with excess borate [90]. 

The trp repressor controls the operon for the synthesis of L-tryptophan in Escherichia coli by a simple negative feedback loop. In the absence of L-tryptophan, the repressor is inactive, the operon is switched on and the enzymes which synthesize L-tryptophan are produced. As the concentration of L-tryptophan increases, it binds to the repressor and converts it to an active form so that it can bind to the operator region and switch off the gene. 

Since 1978, several papers have examined the potential of using immobilised cells in fuel production. Microbial cells are used advantageously for industrial purposes, such as Escherichia coli for the continuous production of L-aspartic acid from ammonium fur-marate.5,6 Enzymes from microorganisms are classified as extracellular and intracellular. If whole microbial cells can be immobilised directly, procedures for extraction and purification can be omitted and the loss of intracellular enzyme activity can be kept to a minimum. Whole cells are used as a solid catalyst when they are immobilised onto a solid support. 

The fact that ) -D-galactosidase from Escherichia coli is inactivated more rapidly in the absence of Mg than in its presence can be taken as evidence that the activation of the triazene 38, that is, formation of )5-D-galactosyl-methyldiazonium ion, proceeds without acid catalysis, because Mg is required for the proton-assisted catalysis of yS-D-galactoside hydrolysis by this enzyme.Additional evidence for the absence of acid catalysis in the de-... 

In addition to phosphotriesterase from P. diminuta (PTE) discussed above, two other types of enzymes were found to exhibit phosphotriesterase activity. Interestingly, both are peptidases - the enzymes which in nature hydrolyse a peptide bond. The first one - organophosphorus acid anhydrolase (OPAA) from Alteromonas sp. JD6.5 - is a proline dipeptidase its original activity is to cleave a dipepfide bond with a prolyl residue at the carboxy terminus. The second one - aminopeptidase P (AMPP) from Escherichia coli - is a proline-specific peptidase that catalyses hydrolysis of N-terminal peptide bonds containing a proline residue. ° ... 

A gene (erstEl) encoding a thermostable esterase was isolated from Escherichia coli cells that had been transformed by DNA libraries with metagenomes from environmental samples isolated from thermal habitats. The enzyme belonged to the hormone-sensitive lipase family, could be overexpressed in E. coli, was active between 30 and 95°C, and used 4-nitrophenyl esters with chain lengths of C4-C16 (Rhee et al. 2005). 

D-Aminoacid oxidase has been isolated from a nnmber of yeasts, and the nucleotide sequence of the enzyme from Rhodotorula gracilis ATCC 26217 has been established (Alonso et al. 1998). The gene could be overexpressed in Escherichia coli, and levels of the enzyme were greater under conditions of low aeration the enzyme isolated from the recombinant organisms was apparently the apoenzyme since maximum activity required the presence of FAD. 

The gene encoding the esterase from Pseudomonas fluorescens was expressed in Escherichia coli, and the enzyme displayed both hydrolytic and bromoperoxidase activity (Pelletier and Altenbnchner 1995). 

Exceptionally, in Escherichia coli acireductone dioxygenase (enediol dioxygenase) carries out two enzymatic activities that are responsible for the salvage of methionine, but are encoded by the same gene. Whereas one enzyme is dependent on Fe and produces the ketoacid and formate (Figure 3.34a), the other that is nickel-dependent produces the carboxylic acid, formate, and CO (Figure 3.34b) (Dai et al. 1999). 

Ratnatilleke A, JW Vrijbloed, JA Robinson (1999) Cloning and sequencing of the coenzyme B,2-binding domain of isobutyryl-CoA mutase from Streptomyces cinnamonensis. Reconstitution of mutase activity and characterization of the recombinant enzyme produced in Escherichia coli. J Biol Chem 274 31679-31685. 

---