Bacterial enzymes, degradation

Alcohol and alcohol ether sulfates are commonly considered as extremely rapid in primary biodegradation. The ester linkage in the molecule of these substances, prone to chemical hydrolysis in acid media, was considered the main reason for the rapid degradation. The hydrolysis of linear primary alcohol sulfates by bacterial enzymes is very easy and has been demonstrated in vitro. Since the direct consequence of this hydrolysis is the loss of surfactant properties, the primary biodegradation, determined by the methylene blue active substance analysis (MBAS), appears to be very rapid. However, the biodegradation of alcohol sulfates cannot be explained by this theory alone as it was proven by Hammerton in 1955 that other alcohol sulfates were highly resistant [386,387]. 

Uchida E, T Ouchi, Y Suzuki, T Yoshida, H Habe, I Yamaguchi, T Omori, H Nojiri (2005) Secretion of bacterial xenobiotic-degrading enzymes from transgenic plants by an apoplastic expression system applicability for phytoremediation. Environ Sci Technol 39 7671-7677. 

Biodegradable drilling fluid formulations have been suggested. These are formulations of a polysaccharide in a concentration insufficient to permit a contaminating bacterial proliferation, namely a high-viscosity carboxymethyl-cellulose sensitive to bacterial enzymes produced by the degradation of the polysaccharide [1419]. 

Three cyanide-degrading nitrilases were recently cloned and purified and their kinetic profiles were evaluated in order to better understand their applicability to cyanide bioremediation. CynD from Bacilluspumilus Cl and DyngD from Pseudomonas stutzeri exhibit fairly broad pH profiles with >50% activity retained across pH 5.2 to pH 8.0 while the CHT (NHase) from Gloeocercospora sorghi exhibited a more alkaline pH activity profile with almost all of its activity retained at pH 8.5, slightly lower thermal tolerance, and quite different metal tolerance compared with the two bacterial enzymes [46]. 

The bacteria in the intestinal tract serve as another well-known source of luminal drug degradation [61], though this is only important for the colon region as the luminal concentration of bacteria is 104 to 109-fold higher in the colon compared with the small intestine. Thus, this aspect is only relevant for drugs that reach this region, for example, due to poor permeability, slow dissolution or delivery by modified-release formulations. Hydrolytic and other reductive reactions are predominantly mediated by bacterial enzymes, and a list of the most prominent types... 

In this chapter we describe the use of pea seeds to express the bacterial enzyme a-amylase. Bacterial exoenzymes like the heat stable a-amylase from Bacillus licheni-formis are important for starch hydrolysis in the food industry. The enzymatic properties of a-amylase are well understood [13,14], it is one of the most thermostable enzymes in nature and it is the most commonly used enzyme in biotechnological processes. Although fermentation in bacteria allows highly efficient enzyme production, plant-based synthesis allows in situ enzymatic activity to degrade endogenous reserve starch, as shown in experiments with non-crop plants performed under greenhouse conditions [12,15]. Finally, the quantitative and sensitive detection of a-amylase activ-... 

Most of this chapter (Sect. 5.2) focuses on the chemical reactivity of the lactam bond and its hydrolysis by bacterial enzymes (lactamases), rather than to its metabolic degradation by mammalian enzymes. This is in contradistinction to other chapters of this book, where metabolism in mammals is the focus of discussion. The reason for the attention given here to the chemical reactivity and bacterial degradation of /3-lactams is that these issues have caused more pharmaceutical and clinical problems than metabolic hydrolysis. This also explains why the chemical stability of /3-lactams and their resistance to /3-lactamases have been the subject of countless studies, while the metabolism of these compounds has received less attention. 

Attempts have been made to achieve colon-speeifie delivery of drugs. These include prodrugs and enteric coated polymers that are sensitive to degradation by bacterial enzymes, and matrices and hydrogels suseeptible to degradation by baeterial enzymes. 

Matrix and Hydrogels Susceptible to Degradation by Bacterial Enzymes... 

On the basis of this anti-proteolytic effect of sialic acids, a hypothetical model435 for the role of sialidase in clostridial infections is shown in Scheme 4. It is considered that the bacterial enzyme releases sialic acids from cell-surface glycoproteins of the infected tissue, which thereafter can be readily attacked by proteases. This cooperation between sialidase and protease may support the spreading of the bacteria. Acylneuraminate pyruvate-lyase, also shown in this model, degrades sialic acids for energy supply, and growth, of the bacteria. 

Oxalocrotonate tautomerase. This bacterial enzyme, which functions in the degradation of toluene (Chapter 25), is actually an isomerase. It catalyzes rapid interconversion of an unconjugated unsaturated a-oxoacid such as 4-oxalocrotonate with an intermediate enol (which may leave the enzyme) and the isomeric conjugated oxoacid (Eq. 13-31).168-170 A related 5-carboxymethyl-2-hydroxymuconate isomerase... 

The extracellular polysaccharides of Rhizobium meliloti 201 have been examined by using enzymic degradation and chemical procedures.314 A mixture of polysaccharides produced by the bacterium, when incubated with a bacterial enzyme that hydrolyzed one of these, gave oligosaccharides that could be separated by DEAE-cellulose chromatography. The major fraction was a pentasaccharide, for which methylation analysis and Smith... 

Yet little if any pectin can he recovered in the stool, due to rapid digestion by bacterial enzymes present in the colon. Breakdown products include galacturonic acid, volatile acids such as formic and acetic, and finally, carbon dioxide and water. Although galacturonic acid is not absorbed by the human ileum or colon, it does not appear in the feces (54). Apparently this acid is further degraded to acetic and formic acids, which have been seen to increase in fecal excretion of subjects fed 30 g of pectin daily. 

One of the first examples is a polymer network that consists of polyvinylalco-hol crosslinked by a thrombin-degradable peptide-linker [108] and the encapsulated antibiotic Gentamycin. In the case of a wound infection, the thrombin content increases dramatically. This enzyme degrades the co-network, and releases the Gentamycin, which then fights a possible bacterial infection (see Fig. 7). Suzuki and Tanihara have shown that the antibiotic is only released in the presence of thrombin and only then effectively kills S. aureus and P. aeruginosa cells [109, 110],... 

Enzyme-Degradable Hydrogel. Because lysozyme is a well characterized enzyme, our first choice was a lysozyme-degradable hydrogel (11, 12). The natural substrate for lysozyme is chitin (13). but because chitin is a rigid, hydrophobic material, it is clearly not suitable for this work. The other natural substrates for lysozyme are certain bacterial cell-wall peptidoglycans (13. 

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