Protein tyrosine phosphatases (PTPases) are a general class of enzymes that are

Question

Protein tyrosine phosphatases (PTPases) are a general class of enzymes that are involved in a variety of disease processes including diabetes and obesity. In a study by Z.-Y. Zhang and coworkers [J. Medicinal Chemistry 43 (2000): 146], computational techniques were used to identify potential competitive inhibitors of a specific PTPase known as PTP1B. The structure of one of the identified potential competitive inhibitors is shown here: The reaction rate was determined in the presence and absence of inhibitor I and revealed the following initial reaction rates as a function of substrate concentration: Determine K_m and R_max for PTP1B. Demonstrate that the inhibition is competitive, and determine K_i.

Explanation / Answer

from the plot of 1/V = (KM/Vmax)*1/S +1/Vmax

KM/Vmax =slope for no inhibition, 1/Vmax= intercpet

from the plot, 1/Vmax = 1.281, Vmax = 1/1.281 = 0.78064uM/s, Km/Vmax= slope = 4.013, KM= 4.013*0.78064=3.13 ( No inhibition)

since intercpet in the presence of inbitior remained same, it is competitie inhiibtion.

for competrivie inhibition 1/V= 1/Vmax + (KMapp/Vmax )*1/S

KMapp = (1+I/KI)*KM

from the plot for inhibition = (1+I/KI)*KM= 16.31

1+I/KI = 16.31/3.13= 5.2

I/KI= 4.2

KI= !/4.2 = 200um/4.2 = 47.62 uM

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