Hydrolysis by enzymes

The renewal of tissue lipids involves their preliminary intracellular hydrolysis by enzymes. 

By keeping the same fluorophores, but reducing the cavity size of the ion-ophore, we obtain PCT-13 (Mag-Indol) and PCT-14 (Mag-Fura2) (Figure 10.22), which are selective for magnesium. PCT-8, PCT-9 and PCT-11 to PCT-14 are commercially available in the non-fluorescent acetoxymethylester form so that they are cell permeant and they recover their fluorescence upon hydrolysis by enzymes (Molecular Probes, Inc., Eugene, OR). 

By comparing the chromatogram from enzymatic hydrolysis with that in the absence of enzymatic hydrolysis, the completeness of hydrolysis by enzymes and the total isoflavones in soy food extract can be determined (see Basic Protocol 3). 

It appears to the author that the existence of a distinct glucose-6-phosphatase is well established for endoplasmic reticulum of liver, kidney, small intestine, and pancreas but additional studies appear to be required before a similar conclusion may be reached regarding the enzyme from other sources. It should be pointed out, however, that while glucose-6-P hydrolysis by enzymes from many sources may not result from specific glucose-6-phosphatase, this hydrolysis in these tissues may nonetheless be of metabolic significance. 

In the filters, their hydrolysis by enzymes (such as lysozyme which catalyses the cleavage of the muramic acid and the N-acetyl glucosamine molecules) may also release amino acids or peptides [16]. 

Table III. Insecticide Hydrolysis by Enzymes of Mammals and Resistant Arthropods...

In addition to chemical hydrolysis, hydrolysis by enzymes can operate as an alternative degradation process. It has become widely accepted that biodegradable synthetic polymers tend to be designed to mimic those structures prevailing in nature, since enzymes produced by microbial populations may not discriminate between polymers of similar structure.11 Synthetic nonpolypeptidic, chiral polyamides could mimic natural peptides or proteins, resulting in biodegradable products useful in biomedicine. 

Fig. 9. Proposed DNA phosphate hydrolysis by enzymes containing dinuclear metal centers, via two-metal-ion assisted phosphoryl transfer. Solid lines indicate the geometry around the central phosphorus atom. Charges on oxygen atoms and metals have been omitted.

In contrast to the fractions M-la and M-Ib isolated from the extracellular acid phosphatase of tobacco XD-6 cells, which had maximum activity at pH 6.8, the fraction M-//exhibited a pH optimum at 5.8, indicating an acid phosphatase. When a temperature of 55°C (instead of 30°C) was used for the para-nitrophenyl phosphatase activity of the three enzyme fractions from phosphate-supplied culture, the activity of M-la was rather stable, whereas fractions M-lb and M-11 were inactivated by about 35% and 90%, respectively, in 30 min. The Lineweaver-Burk plot of the rate of para-nitrophenyl phosphate hydrolysis by enzyme fractions from a phosphate-supplied culture showed that the apparent Michaelis constant of fractions M-la and M-lb was 0.9 mM, whereas that of M-11 was 0.3 mM (Ninomiya et al., 1977). 

The synthetical polypeptides are completely hydrolysed by boiling with concentrated hydrochloric acid for five hours lO per cent, hydrochloric acid at 100° C. hydrolyses them very slowly, and normal alkali has only a very slight action. Their hydrolysis by enzymes, especially by trypsin, is of such importance that a special section is required for the description of these results. 

Dietary fibers represent a gronp of carbohydrates, isolable from different plant sources, that are resistant to hydrolysis by enzymes of the gastrointestinal tract. They are divided into two groups water soluble fibers, among which the main are the p-glncans and arabinoxylans, and water insoluble fibers, which include lignins, celluloses, and hemicelluloses. 

Qing Q, Yang B, Wyman CE. (2010). Xyloohgomers are strong inhibitors of cellulose hydrolysis by enzymes. Bioresour Technol, 101(24), 9624—9630. 

Now that we have seen examples of hydrolytic reactions and acetal hydrolysis by enzymes, we may wonder how important the stereochemistry of the products and reactants is in these transformations. 

White, or yellow, mustard (5. alba) contains the glucosinolate sinalbin, which on hydrolysis by enzymes present (myrosin or glucosinolases) yields /i-hydroxybenzyl isothiocyanate (a relatively nonvolatile compound), -hydroxybenzylamine, and other similar components (proteins, fixed oils, sinapine, rhamnogalacturonan mucilage, etc.) as brown mustard (jiangsu marsh). 

Hydrolysis by enzymes (free or immobilized car-bohydrases) is characterized by rapidly decreasing the energy of activation of the (thermodynamically possible) reaction. So, processing under mild energetic and environmentally suitable conditions becomes possible. 

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