The MWC model postulates that all subunits in an enzyme oligomer change conformation in a concerted fashion, while the KNF model assumes this change may be sequential for the different subunits. Most K-type enzymes have positive cooperativity; a limited number of regulatory enzymes have negative cooperativity. This controlled change in affinity makes the enzyme more sensitive to changes in substrate concentration (positive cooperativity), or dampens the enzyme’s response to changes in substrate concentration (negative cooperativity). When multiple enzymes work in concert for some cellular process, and are regulated in concert by the same original effector, this may produce very high ultrasensitivity.
KeywordsSubstrate Concentration Purine Nucleoside Phosphorylase Positive Cooperativity Hyperbolic Curve Negative Cooperativity
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