Enzymatic measurement

Edsall, L.C. and Spiegel. S., 1999, Enzymatic measurement of sphingosine 1-phosphate,... 

Fig.1.4.3 Reactions involved in the enzymatic measurement of 3-hydroxybutyrate, acetoacetate, lactate and pyruvate...

Porter JL, Fordtran JS, Santa Ana CA, Emmett M, Hagey LR, Macdonald EA, Hofmann AF (2003) Accurate enzymatic measurement of fecal bile acids in patients with malabsorption. J Lab Clin Med 141 411-418... 

Qureshi MY, Smith SM, Murphy GM (1984) Colorimetric enzymatic measurement of serum total -hydroxy bile acid concentrations without extraction. Clin Pathol 37 317-320... 

In the Basic Protocol, gas-liquid chromatography (GLC) using an open tubular wall, coated, fused silica column with nonpolar liquid phase is described. In Alternate Protocol 1, reversed-phase HPLC (RP-HPLC) is applied for separation and quantification of cholesterol. In Alternate Protocol 2, enzymatic measurement is applied for determination of cholesterol. 

ALTERNATE PROTOCOL 2 ENZYMATIC MEASUREMENT OF CHOLESTEROL Test combination kits for enzymatic determination of cholesterol in food are now commercially available. For the determination of total cholesterol, esterified cholesterol is hydrolyzed to free cholesterol and fatty acid under mild alkaline conditions. Cholesterol oxidase oxidizes free cholesterol to cholest-4-en-3-one to generate hydrogen peroxide, which further oxidizes methanol to formaldehyde. Formaldehyde then reacts with acetyl acetone in the presence of NH4+ ions to form yellow lutidine dye, which is subsequently determined spectrophotometric al 1 y. 

Table D1.3.1 Sample Dilution for Enzymatic Measurement cf Cholesterol...

Cholesterol oxidase shows relatively wide substrate specificity to 3(3-sterol analogs as shown in Table Dl.3.5 As discussed above, cholesterol contents of certain shellfish, which contain a relatively large amount of 3[3-sterol analogs, may be unreliable when determined by the enzymatic measurement as compared to results found using GC measurement, as shown in Table D 1.3.6 (Kushiro et al., 1980). 

Preparation of the sample for enzymatic measurement requires <30 min. One measurement requires <70 min. 

Apart from this, AT-methylhydantoin amidohydrolase is also useful for diagnostic purposes. JV-Methylhydantoin amidohydrolase and the corresponding enzyme in microbial creatinine transformation [i.e. N-carbamoylsarcosine amidohydrolase (EC 3.5.1.59)] are useful for enzymatically measuring creatinine in serum and urine, which is a marker of renal dysfunction [12]. This enzymatic method has proved to be simple and precise, and shows excellent sensitivity and specificity [38],... 

E. P. Marbach and M. H. Weil, Rapid enzymatic measurement of blood lactate and pymvate Use and significance of metaphosphoric acid as a common precipitant, Clin. Chem. 13 (1967), 314-325. 

Mayzaud, P. (1987). Enzymatic measurements of metabolic processes concerned with respiration and ammonia excretion. In Biological Chemistry of Marine Copepods (Comer, E. D. S., and O Hara, S. C. M., eds.). Clarendon Press, Oxford, pp. 226-259. 

Note Kodak Research Laboratories developed a slide for enzymatic measurement of CO2 (E664, EN29, EN46, EN56, EN94). 

Deneke, U., Rittersdorf, W. and Werner, W. (1985). Performance data of Reflotron GOT (AST) dry chemistry test for Reflotron. Clin. Chem. 31,92i, Abstr. 96. Frey, G., Berger, D. and Werner, W. (1985). Enzymatic measurement of creatinine in whole blood with Reflotron. Clin. Chem. 31, 922, Abstr. 99. 

Specimen tubes should be centrifuged with stoppers in place. Closure reduces evaporation, which occurs rapidly in a warm centrifuge with the air currents set up by centrifugation. Stoppers also prevent aerosolization of infectious particles. Specimen tubes containing volatiles, such as ethanol, must be stoppered while they are spun. Centrifuging specimens with the stopper in place maintains anaerobic conditions, which are important in the measurement of carbon dioxide and ionized calcium. Removal of the stopper before centrifugation allows loss of carbon dioxide and an increase in blood pH. Control of pH is especially important for the enzymatic measurement of acid phosphatase, which is labile under alkaline conditions engendered by CO2 loss. Indeed, once the serum is separated for acid phosphatase tests, a tablet of disodium citrate should be added to stabilize the pH at about 6.2. 

Enzymes from a number of metabolic pathways have been investigated for the enzymatic measurement of creatinine. AU of the methods involve a multistep approach leading to a photometric equilibrium (Figure 24-1). There are primarily three approaches, described below. ... 

Fossati P> Ponti M, Passoni G, Tarenghi G, Melzi d Eril GV, Prencipe L. A step forward in enzymatic measurement of creatinine. Clin Chem 1994 40 ... 

Jones GW, Ashwood ER. Enzymatic measurement of phosphatidylglycerol in amniotic fluid. Clin Chem 1994 40 518-25. 

To simplify the enzymatic measurement of glucose, Free et al. (1956) adopted the principle of the litmus paper used for pH measurement. By impregnating filter paper with the glucose-converting enzymes they obtained the first enzyme test strip which can be regarded as the predecessor of optoelectronic biosensors and which initiated the development and application of dry chemistry . Nowadays highly sophisticated enzyme test strips are commercially available for the determination of about 15 different low molecular weight metabolites as well as the activities of 10 enzymes. 

In fact, it is remarkable that the agreement between the dynamic and static measurements is so close in defining the sequence of events in the hydration process as noted above, NMR, dielectric relaxation, ESR, and enzymatic measurements each define one or more of the steps in the hydration process seen in static measurements. 

Carerl, G.C. Gratton, E. Yang, P.-H. Rupley, J.A. "Protein-Water Interactions. Correlation of Infrared Spectroscopic, Heat Capacity, Diamagnetic Susceptibility and Enzymatic Measurements on Lysozyme Powders," submitted for publication, 1979. 

Enzymatic measurement of xvlulose-Po in inhibitor preparations Xylulose-P2 is a... 

Carbohydrates were extracted by Methanol, Chloroform, water (12/5/3, in 300 pi) and the water soluble fraction was analysed and quantified by HPLC. Starch was determined after treatment by 0.02 N NaOH, digestion by amyloglucosidase and enzymatic measurement of glucose. 

Of the esters, starch phosphate is produced by reaction with phosphorus oxychloride, polyphosphates, or metaphosphates a cross-bonded product results. Total degree of substitution is determined by measuring the phosphorus content, and the mono- to disubstitution ratio can be calculated by potentio-metric titration. Allowance is made for the natural phosphorus content of the starch. Treatment of starch with acetic anhydride produces starch acetate, which has improved paste stability over native starch. The acetyl group is very labile, and hydrolyses readily under mild alkaline conditions. When a known amount of alkali is used, the excess can be titrated and the ester function measured. This is not specific, however, and a method based on an enzymatic measurement of the acetate has been developed in an ISO work group. The modified starch is hydrolyzed under acidic conditions, which releases acetic acid and permits filtration of the resulting solution. Acetic acid is then measured by a commercially available enzyme test kit. Both bound and free acetyl groups can be measured, and the method is applicable... 

A more specific type of chemical assay is based on enzymatic measurement of vitamin co-enzyme activity. This approach is designed to detect a vitamin deficiency in tissues, and is only feasible for those vitamins that serve as co-enzymes. For instance, thiamin depletion in a subject can be diagnosed by measuring the transketolase activity in red blood cells with and without the addition of thiamin pyrophosphate (TPP) in vitro. If TPP increases the activity by more than a given amount, thiamin deficiency is indicated. Similarly, a subnormal level of riboflavin is indicated in tissues if the activity of erythrocyte glutathione reductase is increased after the addition of flavin adenine dinucleotide (FAD). Erythrocyte transaminase activation by pyridoxal-5 -phosphate (PLP) can be measured to establish a deficiency of vitamin B . 

Other blood constituents have also been measured. Blood lactate measurements were reported by Lafrance et al. with very high correlation compared with enzymatic measurements [195]. Kuenstner et al., in several papers, focused on the determination of hemoglobin levels [196-198]. Predictions of globulin, urea, albumin, and cholesterol have also been reported [199]. Note that in vivo lactate measurements were also published [200]. 

For 1-pentanol at a surfactant concentration of 8% a/ value of 0.6 is found, which is clearly higher than the value of 0.4 inferred from NMR. So all that can be inferred from the enzymatic measurements is that approximately one half of the alcohol molecules is incorporated in the micellar pseudophase. 

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