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Enzymes international unit

R12. Rice, E. W, Standardization of ceruloplasmin activity in terms of international enzyme units. Ann. Biochem. 3, 452 (1962). [Pg.62]

An older term, the International Enzyme Unit (lU), is defined as the amount of enzyme which will catalyse the transformation of 1 pmol of substrate min under standard conditions. [Pg.66]

By international agreement, 1.0 unit of enzyme activity is defined as the amount of enzyme causing transformation of 1.0 gmol of substrate per minute at 25 °C under optimal conditions of measurement. The term activity refers to the total units of enzyme in a solution. The specific activity is the number of enzyme units per milligram of total protein (Fig. 3-23). The specific activity is a measure of enzyme purity it increases during purification of an enzyme and becomes maximal and constant when the enzyme is pure (Table 3-5). [Pg.94]

The lipase used was isolated from Pseudomonas tluorescens and was commercially available from Amano International Enzyme Co., Inc. (Troy, VA) as a powder, specific activity 32,000 units/g (P-30). [Pg.6]

The question of the enzyme units was reexamined by the commission of clinical chemistry of the I.U.P.A.C. The recommendations made appeared in a monograph of R. Dybkaer and EL Jtttgensen, "Quantities and Units in Clinical Chemistry. Cooenhaaen 1967 " Some formal imnerffictions of the international... [Pg.337]

Calculation One unit of enzyme activity (FIP Unit) is defined as that quantity of a standard lipase preparation (Fungi Lipase-International FIP Standard) that liberates the equivalent of 1 (imol of fatty acid per minute from the Substrate Emulsion under the described assay conditions. The specific activity is expressed in international FIP units per milligram of the Sample Preparation. [Pg.915]

The International Enzyme Commission recommends that the enzyme unit should be defined as 1 /zmole of D-glucosidic bond attacked per minute, under conditions of optimal pH and substrate concentration, at 25° (where practicable). [Pg.324]

The enzyme activity is defined as the moles of substrate or product converted in a reaction per time unit. The enzyme activity depends on the reaction conditions, which should be specified. In the International system (SI) the unit is the katal (i katal=1 mol/s) but a more practical and commonly used value is 1 enzyme unit (U) =l imol/min. One enzyme unit corresponds to 16.67 nanokatals [7]. [Pg.177]

Enzyme activities are expressed generally as international units one unit is the amount of enzyme that will catalyze under optimum conditions the transformation of 1 pmol of substrate per minute. The activities are expressed as lU/L or mLU/ mL. The katal (kat nanokatal = nKat) has been proposed as an alternative unit it is defined as the catalytic activity that, under dehned conditions, converts 1 mol of substrate per second. Thus, the units are moles per second (mol/s). One lU/L corresponds to 16.67 nKat/L. Unfortunately, these dehnitions of enzyme units do not include other major variables that affect their measurement, such as the composition and pH of buffer, identity and concentration of the substrate, temperature, and the presence of activators. This has led to a variety of national and international recommendations for the common enzyme measurements, which confuse comparisons between published data. Calibration of enzyme methodologies— particularly for less common enzymes— remains a laboratory issue (Jansen et al. 2006). [Pg.22]

Describe significant phenomena (see Table 4.1) case 1, transports RTD, mixing, CTD, OTR, H TR, and so on, and/or case 2, metabolic rates significant and compositional changes in cell content, for example, proteins, DNA, RNA, enzymes, macromolecules such as PHB, as internally balanced units together with macroscopic process variables. [Pg.141]

Yanofsky, C. (1956) Gene interactions in enzyme synthesis. In Enzymes Units of Biohgical Structure and Function, Henry Ford Hospital International Symposium, pp. 147-160, Acadranic Press. [Pg.270]

For purposes of dosage, the specific activity of an enzyme is usually expressed as International Units (lU) rather than in terms of weight. However, unit measurements do not provide information on the absolute purity of a given product. Moreover, purity is not as critical an attribute for oral enzymes, as opposed to those adrninistered parenteraHy, inasmuch as the gastrointestinal tract is capable of disposing of most inert contaminants. [Pg.313]

Enzymes are excellent catalysts for two reasons great specificity and high turnover rates. With but few exceptions, all reac tions in biological systems are catalyzed by enzymes, and each enzyme usually catalyzes only one reaction. For most of the important enzymes and other proteins, the amino-acid sequences and three-dimensional structures have been determined. When the molecular struc ture of an enzyme is known, a precise molecular weight could be used to state concentration in molar units. However, the amount is usually expressed in terms of catalytic activity because some of the enzyme may be denatured or otherwise inactive. An international unit (lU) of an enzyme is defined as the amount capable of producing one micromole of its reaction product in one minute under its optimal (or some defined) reaction conditions. Specific activity, the activity per unit mass, is an index of enzyme purity. [Pg.2149]

In many situations, the actual molar amount of the enzyme is not known. However, its amount can be expressed in terms of the activity observed. The International Commission on Enzymes defines One International Unit of enzyme as the amount that catalyzes the formation of one micromole of product in one minute. (Because enzymes are very sensitive to factors such as pH, temperature, and ionic strength, the conditions of assay must be specified.) Another definition for units of enzyme activity is the katal. One katal is that amount of enzyme catalyzing the conversion of one mole of substrate to product in one second. Thus, one katal equals 6X10 international units. [Pg.438]

In each of the assays of potency the amount of the immunoglobulin and the amount of a corresponding standard preparation that are required to neutralize the infectivity or other biological activity of a defined amount of virus or to neutralize a defined amount of a bacterial toxin are determined. The two determined amounts and the assigned unitage of the standard preparation are then used to calculate the potency of the immunoglobulin in International Units (lU). ELISA, enzyme-linked immunosorbent assay. [Pg.319]

In addition to KM and vmax, the turnover number (molar activity) and the specific activity are two important parameters in enzyme catalyzed reactions. The turnover number indicates the number of substrate molecules converted per unit time by a single enzyme molecule. The specific activity is given in units and one international unit (i.u.) is the amount of enzyme that consumes or forms 1 pmol of substrate or 1 pmol of product per minute under standard conditions. [Pg.337]

Most patients with malabsorption require pancreatic enzyme supplementation (Fig. 28-2). The combination of pancreatic enzymes (lipase, amylase, and protease) and a reduction in dietary fat (to less than 25 g/meal) enhances nutritional status and reduces steatorrhea. An initial dose containing about 30,000 international units of lipase and 10,000 international units of trypsin should be given with each meal. [Pg.324]


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See also in sourсe #XX -- [ Pg.259 ]

See also in sourсe #XX -- [ Pg.66 ]




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