Standard enzyme unit (U, unit) or activity:<\/strong><\/p>\n\n\n\n One unit (U) is the amount of enzyme activity which will <\/em>catalyse<\/em> the transformation of 1 micromole of the substrate per minute under standard conditions.<\/em><\/p>\n\n\n\n One <\/em>katal<\/em> (<\/em>kat<\/em>) is that catalytic activity which will raise the rate of reaction by one mole per second in a specified assay system.<\/em><\/p>\n\n\n\n Specific enzyme activity:<\/strong><\/p>\n\n\n\n activity per unit protein amount (U\/mg). It is a useful term to follow purification of enzymes<\/em><\/p>\n\n\n\n Catalytic constant or turnover number:<\/strong><\/p>\n\n\n\n a maximum number of substrate molecules that an enzyme can convert to product per catalytic site per unit time: Its dimension is s-1. It shows how fast the enzyme is when its active centre is saturated with substrate.<\/p>\n\n\n\n <\/div><\/p>\n\n\n\n Due to the fact that the enzymes are proteins, the parameters which are affecting the activity of the enzymes are:<\/p>\n\n\n\n It is the substrate concentration when the rate is half of the Vmax.<\/strong><\/p>\n\n\n\n A typical example of the difference in the KM value: hexokinase – glucokinase (Figure 3).<\/p>\n\n\n\n It is the reaction rate when the active site of the enzyme is saturated with substrate, i.e. [S] >> KM<\/sub>, [ES] = [Et]<\/strong><\/p>\n\n\n\n For the validation and determination we can use two optional representations:<\/p>\n\n\n\n plots.<\/p>\n\n\n<\/span>\n Figure 5. Lineweaver – Burk plot.<\/strong> he Lineweaver-Burk plot puts 1\/[S] on the x-axis and 1\/V on the y-axis. The Lineweaver\u2013Burk plot was widely used to determine important terms in enzyme kinetics, such as K<\/em>m<\/em><\/sub> and V<\/em>max<\/sub>. The y<\/em>-intercept of such a graph is equivalent to the inverse of V<\/em>max<\/sub>; the x<\/em>-intercept of the graph represents \u22121\/K<\/em>m<\/em><\/sub>. It also gives a quick, visual impression of the different forms of enzyme inhibition.<\/p>\n\n\n<\/span>\n Figure 6. The Michaelis – Menten<\/strong> model takes the form of an equation describing the rate of enzymatic reactions, by relating reaction rate The problem with the previously mentioned methods that there requires a constant level of the substrate, which is not every time true. The correct representation shows the decay of the substrate while the product amount is increasing. (Figure 7)<\/p>\n\n\n\n <\/p>\n<\/span>Environmental parameters<\/h2>\n<\/span>\n\n\n
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DETERMINATION OF KM<\/sub> AND Vmax<\/sub> – THE MEANING OF KM<\/sub><\/h2>\n<\/span>\n\n\n
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<\/a><\/a>DETERMINATION OF KM<\/sub> AND Vmax<\/sub> – THE MEANING OF VMAX<\/sub><\/h2>\n<\/span>\n\n\n
<\/a>DETERMINATION OF KM<\/sub> AND Vmax<\/sub> – Lineweaver-Burk (double reciprocal) plot<\/h2>\n<\/span>\n\n\n
<\/a><\/figure>\n\n\n\nMICHAELIS-MENTEN KINETIC MODEL<\/h2>\n<\/span>\n\n\n
<\/a><\/figure>\n\n\n\nBRIGGS-HALDANE (STEADY STATE) KINETICS<\/h2>\n<\/span>\n\n\n
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