The kinetic behaviour of enzymes is typically observed in conditions appropriate for studying questions of mechanism of action, but these are not necessarily the most appropriate for studying their physiological roles, because they are often too far from those that exist in the living organism. Enzymes therefore need to be studied with natural substrates in the presence of all of the other small molecules likely to affect the activity in vivo, including the reaction products, so that the reverse reaction is not artificially prohibited. As complete reversible rate equations are often unmanageably complicated, especially for cooperative kinetics, care needs to be taken in choosing simpler equations that preserve the properties that are relevant in physiological conditions.

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