Enzymes enzyme ratios

A pepsin hydrolysate of flounder fish protein isolate has been used as the substrate (40% w/v) for plastein synthesis, using either pepsin at pH 5 or alpha chymotrypsin at pH 7, with an enzyme—substrate ratio of 1 100 w/v at 37°C for 24 h (151). The plastein yields for pepsin and alpha chymotrypsin after precipitation with ethanol were 46 and 40.5%, respectively. 

Pancreatic enzyme replacement is the mainstay of gastrointestinal therapy. Most enzyme products are formulated as capsules containing enteric-coated microspheres or microtablets to avoid inactivation of enzymes in the acidic stomach instead, they dissolve in the more alkaline environment of the duodenum. Capsules may be opened and the microbeads swallowed with food, as long as they are not chewed. A powder form is available for patients unable to swallow the capsules or microbeads, but bioavailability is poor. While products may contain similar enzyme ratios, they are not bioequivalent and cannot be substituted. Generic enzyme products generally display poor dissolution and should not be used.5 Table 13-3 lists commonly used enzyme replacement products. 

Type of yeast Method of purification Enzyme value Ratio a/b Enzyme value Ratio c/d... 

Enzyme preparation Ratio of P450 reductase/CYP2C9 Ratio of cytochrome 1>5/CYP2C9... 

Wong" has pointed out that the steady-state approximation only requires that d[BA]/dt be small compared with A i[A][Eq]. In the early phase of the reaction, if [A] [Eo], the rate of change of [EA] due to diminishing [A] will be relatively slow. It is clear that the validity of steady state is intimately tied to the condition of high substrate to enzyme ratio. 

Tissue lysate (or homogenates), post-mitochondrial supernatants and microsomes offer several practical advantages for the study of xenobiotic metabolism. The principal advantages are that the human tissues provide a complete system containing all the enzymes in ratios found in vivo, and tissue fractions are stable in relatively long-term storage. Within the different types of tissue fractions, microsomes provide an enrichment of the membrane-bound enzymes, and post-mitochondrial supernatants provide a means to study both membrane-bound and soluble enzymes. Tissue fractions are easily prepared from a variety of tissues including human liver and can be cryopreserved for several years. This allows detailed characterization of the tissue prior to use with xenobiotics of unknown routes of metabolism... 

Biocatalysis plays a central role in the manufacturing of statin side chains (Figure 6.2). A first set of approaches exploits enzymatic desymmetrization reactions, for example, of the methoxyacetyl ester of glutaric acid diethyl ester with commercially available a-chymotrypsin as explored by Ciba SC with a yield of 94% and enantiomeric excess of up to 98% [1]. In the optimized procedure, the substrate was available in a concentration of 1 M at an enzyme/substrate ratio of 7% (wt/wt), and the reaction took approximately a day. The subsequent steps to the final acetonide also involved a pig-liver esterase (PLE) catalyzed selective hydrolysis of the methoxyacetyl group (Figure 6.2a). 

Figure 6.6 Selwyn inactivation test using ISOOmM acetaldehyde and 600mM ClAA at three different DERA concentrations in the relative enzyme-ClAA ratio 1 ( ) 1.5 ( ) 2 (A).

According to transition state theory, if the transmission coefficient k = 1, T and ET will be transformed to products at the same rate. Thus, if the mechanisms of the nonenzymatic and enzymatic reactions are assumed the same, the ratio of maximum velocities for first-order transformation of ES and S will be given by Eq. 9-85. For some enzymes the ratio... 

NOTE A variety of assay conditions can be used here this protocol is specific for Alcalase. Many other enzymes can be used, as well as other percentages of protein and other enzyme/substrate ratios. 

The mass of enzyme (ME) is based on a recommended enzyme/substrate ratio of 2%. The four-enzyme cocktail (see Reagents and Solutions) has 2.8 mg protein/ml, so a volume of 0.71 ml is needed. At 7 U/ml, this gives 5 U enzyme in the reaction. 

A foodstuff (or other sample) obtained by hydrolysis of a protein material is called a protein hydrolysate. The degree of hydrolysis measures the percentage of peptide bonds hydrolyzed during protein hydrolysis (Adler-Nis-sen, 1976). An advantage of the DH concept is that for a given enzyme/substrate system the DH is independent of five variables substrate concentration, enzyme/substrate ratio, pH. temperature, and time (Adler-Nissen, 1982). 

Scheme I shows the hydrolysis of a phosphate ester in the presence of tris, which can serve as a phosphate acceptor so that O-phosphoryl-tris is a product as well as P(. It has been shown that in the presence of alcohols such as tris and ethanolamine the rate of substrate utilization is increased, that formation of alcohol exceeds that of phosphate, and that the difference is due to the formation of the O-phosphorylamino alcohol (122, 128). The question was Does the reaction with water and with tris emanate from the Michaelis complex or from a phosphoryl enzyme intermediate (E-P) If the reactions with tris and water stem from a phosphoryl enzyme, the ratio of products tris-phosphate and Pi would be independent of the leaving group RO, but if the reactions stem from the reversible complex containing the leaving group, the ratio of products would depend upon the structure of R. It was found that the ratio of free alcohol to phosphate was 2.39 0.02 for nine different substrates, including esters such as p-cresyl phosphate / -naphthyl phosphate, and phosphoenol pyruvate. This experiment established the occurrence of a phosphoryl enzyme intermediate.

Fig. 15. Enzymatic hydrolysis of wheat gluten at 72.5°C and pH 7.5 by an alkaline protease from Bacillus licheniformis. The numbers on the curves are enzyme—substrate ratios (E/S) in activity units (AU)/kg of protein where S = 7.4% (N x 5.7).

Regarding the enzyme polymer ratio, high polymer amounts may provide higher immobilisation yields but may restrict the enzyme flexibility and functionality, and high enzyme amounts may provide higher responses but may limit the sensitivity of the biosensor. The dilemma has appeared and the choice will depend on the own particular interests. The 1 2 ratio provided higher absorbance values (0.259 coefficient of variation (CV) — 17%) than those obtained with the 2 1 (0.041 CY — 9%) and the 1 3 (0.189 CV = 15%) ratios. In the same way, the 1 2 ratio also provided the highest immobilisation yields after 30-min incubation in buffer (62% as compared to 16% and 41% for the 2 1 and the 1 3 ratios, respectively). In our case, the results clearly demonstrate that the 1 2 enzyme polymer ratio is the optimum one for the biosensor construction. 

The membrane has the premier function in the process of biogenesis. It allows for individual ownership and retention of biocatalysts, and thereby for up to a million fold increases in catalytic activity. Substrate/enzyme ratios in cells may approach unity and thus enzymes can actually change the equilibrium of some reactions. Clearly, membranes are essential and the hurdle for nascent life is the need for a selectively permeable membrane... that means a membrane that contains, suspended in its lipid layers, the first communication proteins.13,14 The cell must breathe at once if there is to be any future and that again equalizes units from different clones. Is it surprising then that all life forms have membranes Shapeless wafting life is a thing of poor science fiction. Membrane formation is the moment when life became competitive, it... 

Source of enzyme Ratio of rate of hydrolysis of melibiose to that of phenyl a-D-galactopyranoside... 

Roelofs W. L. and Jurenka R. A. (1996) Biosynthetic enzymes regulating ratios of sex pheromone components in female redbanded leafroller moths. Bioorganic Med. Chem. Letters 4, 461 4-66. 

The redox mediator 2,6-dichlorophenol indophenol, can mediate electron transfer from and to the redox enzyme, cytochrome c. The mediator was switched between the oxidized and reduced forms by the application of a potential using optically transparent electrodes in a thin-layer cell. From the absorbances of the oxidized and reduced form of the enzyme, the ratio of their concentrations at various potentials was obtained. Calculate the formal potential E° of the enzyme from the data given in Table E.l. Confirm that the enzyme redox process involves one electron transfer. (Contractor)... 

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