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The enzyme unit, or international unit for enzyme (symbol U, sometimes also IU) is a unit of enzyme's catalytic activity. [ 1 ] 1 U (μmol/min) is defined as the amount of the enzyme that catalyzes the conversion of one micro mole of substrate per minute under the specified conditions of the assay method .
The katal (symbol: kat) is that catalytic activity that will raise the rate of conversion by one mole per second in a specified assay system. [1] It is a unit of the International System of Units (SI) [1] used for quantifying the catalytic activity of enzymes (that is, measuring the enzymatic activity level in enzyme catalysis) and other catalysts.
Increasing the substrate concentration increases the rate of reaction (enzyme activity). However, enzyme saturation limits reaction rates. An enzyme is saturated when the active sites of all the molecules are occupied most of the time. At the saturation point, the reaction will not speed up, no matter how much additional substrate is added.
The metabolic equivalent of task (MET) is the objective measure of the ratio of the rate at which a person expends energy, relative to the mass of that person, while performing some specific physical activity compared to a reference, currently set by convention at an absolute 3.5 mL of oxygen per kg per minute, which is the energy expended when sitting quietly by a reference individual, chosen ...
Enzyme activity is commonly used for e.g. liver function tests like AST, ALT, LD and γ-GT in Sweden. [ 5 ] Percentages and time-dependent units (mol/s) are used for calculated derived parameters, e.g. for beta cell function in homeostasis model assessment or thyroid's secretory capacity .
in which e is the concentration of free enzyme (not the total concentration) and x is the concentration of enzyme-substrate complex EA. Conservation of enzyme requires that [28] = where is now the total enzyme concentration. After combining the two expressions some straightforward algebra leads to the following expression for the concentration ...
Flux is regulated by the enzymes involved in a pathway. Within cells, regulation of flux is vital for all metabolic pathways to regulate the pathway's activity under different conditions. [1] Flux is therefore of great interest in metabolic network modelling, where it is analysed via flux balance analysis and metabolic control analysis.
The physical activity level (PAL) is a way to express a person's daily physical activity as a number and is used to estimate their total energy expenditure. [1] In combination with the basal metabolic rate , it can be used to compute the amount of food energy a person needs to consume to maintain a particular lifestyle.