Hydrolyzable substrate

Dipeptidyl aminopeptidase IV hydrolyzes substrates with free a-amino groups. Peptide bonds involving the carboxy group of either Pro or Ala are cleaved by this enzyme to X-Pro or X-Ala, where X may be any amino acid. It has been shown that peptides with the X-Pro moiety are hydrolyzed more completely than those with X-Ala [79],... 

Fig. 8a, b. Proposed modes of substrate binding to a PLCBc [45] b PI nuclease [70], based on X-ray structures with non-hydrolyzable substrate analogues... 

Xs = hydrolyzable substrate (gCOD nr3) kH = 1-order hydrolysis constant (d 1)... 

Equation (2.30) describes the two extremes where either availability of hydrolyzable substrate or biomass may limit the hydrolysis. If hydrolyzable substrate is available in excess, i.e., xs>xBw, the biomass density, XBw, is considered proportional to the enzymatic activity, and a situation equivalent to Equation (2.29) exists, i.e., the rate of hydrolysis is 1-order with respect to XBw. Contrarily, if Xs XBw, Equation (2.30) equals Equation (2.28), and the rate of hydrolysis is 1 -order with respect to Xs. Situations between these two extremes are considered appropriately described based on Equation (2.30). 

X particulate substrate (hydrolyzable substrate) available as substrate for the microorganisms after hydrolysis by extracellular enzymes and diffusion of the products into the cell... 

The biodegradability within a period of time corresponding to the residence time in a sewer network (typically between a few hours and one day) must be reasonably detailed. Therefore, the fast biodegradable fractions considered as Ss and fast hydrolyzable substrate must be included as separate fractions. On the contrary, what is not biodegradable within 1-2 days is of minor interest. As a consequence, there is no need to distinguish between a rather slowly biodegradable, particulate fraction of a substrate and a fraction that is inert, whatever it is — soluble or particulate. 

The number of fractions of hydrolyzable substrate is determined by the quality of the wastewater, i.e., when fractions can be identified in terms of their... 

TABLE 5.3. Matrix Formulation of Aerobic Microbial Transformations of Wastewater Organic Matter in a Gravity Sewer (cf. Figure 5.5). The Formulation that is Shown Includes Two Fractions of Hydrolyzable Substrate. 

Anaerobic hydrolysis this process transforms the hydrolyzable substrate, Xsn, into fermentable, readily biodegradable substrate,. S /,. 

The experiment, or preferably a number of parallel experiments, is carried out until the originally available readily biodegradable substrate and the fast hydrolyzable substrate are depleted. For typical domestic wastewater, this is... 

Provided that aerobic conditions exist, the long intercepting sewer is well suited for microbial transformations that support the physicochemical treatment processes. The aerobic removal of readily biodegradable and fast hydrolyzable substrates and the production of slowly biodegradable organic matter in terms of biomass will enhance the efficiency of the entire treatment of... 

The result of the aerobic scenario in terms of quality changes of the wastewater in the intercepting sewer is shown in Table 8.2. The in-sewer treatment is assessed by the changes that take place in the easily biodegradable substrates (readily biodegradable and fast hydrolyzable substrates) and in the... 

The ability of metal ions to accelerate the hydrolysis of a variety of linkages has been a subject of sustained interest. If the hydrolyzed substrate remains attached to the metal, the reaction becomes stoichiometric and is termed metal-ion promoted. If the hydrolyzed product does not bind to the metal ion, the latter is free to continue its action and play a catalytic role. The modus operandi of these effects is undoubtedly as a result of metal-complex formation, and this has been demonstrated for both labile and inert metal systems. Reactions of nucleophiles other than HjO and OH will also be considered. 

Fig. 11. The slowly hydrolyzed substrate glycyl-L-tyrosine binds to carboxypeptidase A in a nonproductive complex where the amino-terminal glycine complexes the active-site ion (large sphere) to form a five-membered chelate, as in Fig. 10. Protein-bound zinc ligands Glu-72, His-69, and His-196 complete the coordinadon polyhedron of pentacoordinate zinc. Active-site residues are indicated by one-letter abbreviadons and sequence numbers E, glutamate H, hisddine R, arginine Y, tyrosine. [Reprinted with permission from Christianson, D. W., Lipscomb, W. N. (1986) Proc. Natl. Acad. Sci. U.S.A. 83,7568-7572.]...

This enzyme is a non-specific phosphomonoesterase that shows maximum activity at pH values greater than 8.569 It also catalyzes the transfer of phosphoryl groups. These reactions involve the formation of a phosphoseryl intermediate and the hydrolyzed substrate. The phosphoenzyme may transfer the phosphoryl group to water or to an acceptor molecule to give a new phosphoester (equations 19 and 20, where E—P represents the covalently bound phosphoenzyme and E-P a non-covalent complex, in which phosphate is coordinated to the zinc). The phosphoenzyme may be formed from either direction. 

Figure 5.2. Monomeric complex 8 hydrolyzes substrate PNPP directly, as the -CH2OH sidearm in the ligand is not involved in the Cu2+-ion coordination. However, the micellar complex 7 is acylated during the hydrolysis of PNPP through its -CH2OH sidearm, which is also involved in the Cu2+-ion binding.

Metal ions are vital to the function of many enzymes that catalyze hydrolytic reactions. Coordination of a water molecule to a metal ion alters its acid-base properties, usually making it easier to deprotonate, which can offer a ready means for catalyzing a hydrolytic reaction. Also, the placement of a metal center in the active site of a hydrolytic enzyme could permit efficient delivery of a catalytic water molecule to the hydrolyzable substrate. In fact, the first enzyme discovered, carbonic an-hydrase, is a metalloenzyme that requires a Zn2+ center for its catalytic activity (32). The function of carbonic anhydrase is to catalyze the hydrolysis of carbon dioxide to bicarbonate ... 

Amongst the D-manno-oligosaccharides, those having a d.p. >2 are hydrolyzed, but the minimum d.p. requirement of a readily hydrolyzable substrate is140,243,253 4. In a detailed study, Villarroya and Petek253 found that the lucerne /3-D-mannanase is unable to hydro-... 

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