An enzyme E binds a substrate S and a cofactor C. The equilibrium dissociation constant Kd,S of the enzyme-substrate complex ES is 1 μM, for EC it is 10 μM. When the cofactor C is present, K’d,S is decreased to 0.1 μM. What is the value for the dissociation constant K’d ,C of the enzyme-cofactor complex in the presence of substrate S? Calculate the interaction energy ΔΔGint for cofactor and substrate binding.
3.18: An enzyme E binds a substrate S and a cofactor C. The equilibrium dissociation constant
Kd,S of the enzyme-substrate complex ES is 1 μM, for EC it is 10 μM. When the cofactor C
is present, K’d,S is decreased to 0.1 μM. What is the value for the dissociation constant K’d
,C of the enzyme-cofactor complex in the presence of substrate S? Calculate the interaction
energy ΔΔGint for cofactor and substrate binding.
Enzymes are usually made of protein molecules which increase the rate of biochemical reaction by decreasing the activation energy of the reaction. It is not consumed in the chemical reaction. Substrate binds to active sites present in the enzymes and catalyzed to produce products. Cofactors are non-proteinaceous molecules that can be of two types - organic molecules called coenzymes or inorganic metal ions like Sn, Cu. It is required by enzymes to work as a catalyst or active form of enzyme or helper of enzymes.
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