Enzyme heat sensitivity

Ultrafiltration (qv) (uf) is increasingly used to remove water, salts, and other low molecular-weight impurities (21) water may be added to wash out impurities, ie, diafiltration. Ultrafiltration is rarely used to fractionate the proteins because the capacity and yield are too low when significant protein separation is achieved. Various vacuum evaporators are used to remove water to 20—40% dry matter. Spray drying is used if a powdery intermediate product is desired. Tyophilization (freeze-drying) is only used for heat-sensitive and highly priced enzymes. 

Although chlorophyll and chlorophyllin colorants seem to be easily obtained, in practice their production as natural food colorants is rather difficult. The sensitivity of chlorophylls to certain enzymes, heat, and low pH, and their low tinctorial strength greatly limit their manufacture and application as food additives, principally when the pigments are isolated from the protective environment of the chloroplasts. The well-known instability of chlorophylls prompted extensive research for developing... 

To overcome this shortcoming, biologists turned to an enzyme that could survive the PCR hot cycle. They replaced the original heat-sensitive enzyme with DNA-polymerase from Thermus acqua-ticus, the Yellowstone extremophile. The new enzyme is unscathed... 

As we saw earlier in this chapter, substrates are the molecules which undergo chemical change as a result of enzyme activity. Many enzymes will only operate when in the presence of essential co-factors or coenzymes. The term coenzyme is not entirely appropriate as it implies that, like enzymes themselves, these compounds do not undergo chemical change. This is not true and more accurate terminology would be co-substrate. Coenzymes are always much smaller than the enzymes with which they operate and are not heat sensitive as are the proteins. 

Pseudomonas and Azotobacter transhydrogenases was provided by Cohen and Kaplan (17) and by van den Broek et al. [19), respectively, who showed that inactivation by heat treatment could be reversed by addition of FAD. FAD could not be replaced by FMN. Reduction of the enzyme with either NADH or NADPH largely increased the heat sensitivity, whereas oxidized nicotinamide nucleotides or FAD had the opposite effect (17, 19). The number of flavins per 50,000-dalton molecular weight was calculated to be 0.58 to 1.1 (17). 

On starch gel electrophoresis, gastricsin migrated 6.5 cm toward the anode after 22 hours as one single narrow band in acetate buffer of pH 5.0. These two materials also differed in heat sensitivity while pepsin at pH 2.0 and 65° C lost 69% of its activity, gastricsin under these conditions lost 44.8%. Conversely, at pH 3.2 pepsin was inactivated only 11.2%, while gastricsin was inactivated 22.3% (Fig. 4). Both enzymes hydrolyzed synthetic carbobenzoxy-glutamyl-L-tyrosine, which is a specific substrate for pepsin. Gastricsin was crystallized as it came from... 

An innovative potential application of membrane technology in catalysis and in CMRs might be the possibility to produce catalytic crystals with a well-dehned size, size distribution, and shape by membrane crystallization [19,20] (Figure 43.5). Membrane crystallization is particularly attractive for the preparation of heat-sensitive catalysts such as enzymes. 

Fruits and vegetables are our primary source of enzymes. However, enzymes are temperature-sensitive, and heat can damage or destroy them. Cooking fruits or vegetables at temperatures above ii8°F, for example, renders the enzymes useless to our bodies. We still benefit from the non-heat-sensitive nutrients and compounds in the produce, but we force our digestive system to work harder with fewer resources. 

Also included are analyses of studies reporting distinctive immunochemical properties as well as physical properties of enzymes prepared from several organs. Separate sections are concerned with electrophoretic data and heat sensitivity. 

In this laboratory, partially purified enzyme preparations from bone, liver, and intestine have been employed in experiments designed to test the quantitative utility of the heat sensitivity. A typical experiment is reproduced in Table 9, and demonstrates the recovery in mixtures of the three organ enzymes. 

Our data support the statement that the heat sensitivity of each enzyme source remains characteristic and independent of the influence of the others in the mixture, and that the resultant heat inactivation is an additive function of the heat-sensitivities of members of the mixture. Bone enzyme from different sources is very consistently heat-sensitive (85-90%), unlike intestinal (50-65%), and liver enzyme (50-75%). However, the heat sensitivity of the LPSAP of normal serum can vary from 33 to 85% and of the non-LPSAP fraction from 50 to 95%. Therefore one cannot determine the identity of the organ sources of serum alkaline phosphatase with a knowledge of only the heat sensitivity and the total alkaline phosphatase. However, by correcting the heat-inactivation of serum by that contributed by intestinal component, one obtains the heat-inactivation of non-intestinal sources of alkaline phosphatase. If this value is 90% or more, the non-intestinal component could be presumed to be of osseous origin if 60% or less, of hepatic origin. 

Starch-gel migration of bone alkaline phosphatase yields bands in locations that can be occupied by gastrointestinal juice alkaline phosphatase as well as by the enzyme of kidney, lung, and spleen. High heat sensitivity is a property of the alkaline phosphatase from these various sources. Hence findings based on starch-gel electrophoresis and heat sensitivity in themselves are not diagnostic of a bone source. 

Canned pineapple has been heated. Enzymes are heat-sensitive, so the proteases in the canned fruit are not active. 

Conditions of Functioning.—Enzymes are sensitive to high temperatures, e.g. when heated to below ioo° C. their activity is completely destroyed. They are, however, resistant to many antiseptics which destroy protoplasm and kill fermenting organisms. Some germicides, such as formaldehyde, tend to destroy. enzymes. 

Pineapple contains bromelain — a proteolytic, or proteinsplitting, enzyme. Enzymes themselves are specialized protein molecules produced by living systems, and they act as biological catalysts that speed up the numerous reactions that together constitute life. The bromelain in pineapple serves as a defense against predators. It irritates the tissues in the mouth as proteins begin to break down. Bromelain, like all enzymes, is heat-sensitive, and cooking destroys it. Canned pineapple is... 

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