Question

In kinetics experiments, the hydrolysis of the substrate sialic acid by neuraminidase appears to obey Michaelis–Menten kinetics. Neuraminidase activity is critical for viral infectivity; thus, this enzyme is the target of much work by pharmaceutical companies to develop a drug to treat influenza virus infection. The drug “Tamiflu” is a competitive inhibitor of neuraminidase. Initial rate data collected at pH=6.15, 37 ∘C with 0.021 μM neuraminidase and 25.0 μM sialic acid gives a Lineweaver–Burk plot with a slope of 51.2 s.

The kcat for neuraminidase at pH=6.15, 37 ∘C is 26.8 s−1. Calculate KM for the hydrolysis of sialic acid.

Express your answer with the appropriate units.

Answer 1

K_M = 28.8 uM

Explanation

Given : k_cat = 26.8 s^-1

enzyme concentration = 0.021 uM

V_max = (k_cat) * (enzyme concentration)

V_max = (26.8 s^-1) * (0.021 uM)

V_max = 0.5628 uM.s^-1

K_M = (slope) * (V_max)

K_M = (51.2 s) * (0.5628 uM.s^-1)

K_M = 28.8 uM