It is very much confusing when some papers use this term "apparent Km of an enzyme even if they use single substrate ? Not at all clear ! Please help me understanding this. Thanks in advance.
Hi there,
The term apparent Km is used basically when the enzyme is not pure and/or when the composition of the reaction mixture is not fully controlled (ie. containing molecules which are not involved directly in the reaction but which may interfere with it): the presence of contaminants during the enzyme assay may affect the results.
Hi there,
The term apparent Km is used basically when the enzyme is not pure and/or when the composition of the reaction mixture is not fully controlled (ie. containing molecules which are not involved directly in the reaction but which may interfere with it): the presence of contaminants during the enzyme assay may affect the results.
Michaelis constants have been determined for many of the commonly used enzymes. The size of Km tells us several things about a particular enzyme.
A small Km indicates that the enzyme requires only a small amount of substrate to become saturated. Hence, the maximum velocity is reached at relatively low substrate concentrations.
A large Km indicates the need for high substrate concentrations to achieve maximum reaction velocity.
The substrate with the lowest Km upon which the enzyme acts as a catalyst is frequently assumed to be enzyme's natural substrate, though this is not true for all enzymes.
The apparent Km assumes the reaction follows all the assumptions of the simplest Michaelis-Menten kinetics model - which for more complex enzymatic mechanism may not be the case Article The apparent K m is a misleading kinetic indicator
You can determine Km if the kinetics is fairly simple and follows the model. If enzyme however is inhibited by substrate itself, i.e. at higher concentration, you would never be able to observe "true" Km, only apparent.
I REALLY appreciate the suggestions given by you all. It was really helpful in understanding what apparent Km means.Sources from internet definitely help but discussion and inputs from scientists have no alternatives so far. Thank you all.
Apparent Km is the Michaelis constant as observed under conditions (e.g. the presence of a competitive inhibitor) that would hinder the determination of its true value; in the case of a two-substrate enzyme, the Michaelis constant measured under the particular conditions of a defined concentration of the invariant substrate. Please keep in mind the contributions of Annemaarie, Marek, Hiba and Liger
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