Q11 - Thiamine Pyrophosphate Enzyme Kinetics in Disease

Theoretical 2 Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license

Many disease causing mutations in enzyme coding genes affect parameters related to interactions of the enzymes with their coenzyme, which in turn lowers the rate of the reaction. The cofactor of a group of enzymes called TPP- or thiamine-dependent enzymes such as transketolase is thiamine pyrophosphate (TPP). The kinetic properties of a TPP-dependent enzyme isolated from a patient’s tissue and a normal individual’s tissue were compared under condition of substrate saturation. The TPP-free forms of the enzyme was prepared and used for enzyme kinetic measurements. The Lineweaver-Burk like plots are shown below.

Figure 1. Figure 1.

Using the information and data, determine which of the statements are true or which are false.

A. A is related to the patient's enzyme.

B. Maximum velocity of B is higher than the maximum velocity of A.

C. It can be concluded that the enzyme in A has a lower affinity for its substrate(s).

D. Administration of thiamine to patients is expected to restore enzymatic activity.

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Question reproduced from IBO 2018, Theoretical Paper 2, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)