Kcat

Practice: To calculate the turnover number of an enzyme, you need to know:

Practice: If 10 μg of an enzyme (MW = 50,000 g/mol) is added to a solution containing a [substrate] 100 times greater than the K_m, it catalyzes the conversion of 75 μmol of substrate into product in 3 min. What is the enzyme’s turnover #?

a) 1.25 x 10⁵ min^-1

b) 2.5 x 10⁴ min^-1

c) 1.5 x 10² min^-1

d) 3.5 x 10⁶ min^-1

Practice: Studies with mutated forms of an enzyme show that changing some active-site amino acids decrease the enzyme’s turnover number (k_cat) but do not affect the K _m of the reaction. What is the best interpretation of these results?

Practice: The turnover number for an enzyme is known to be 5000 min ^-1. From the following set of data, determine both the K_m and the total amount of enzyme E_T.

A) What is the K_m of the enzyme?

a) 1 mM. 

b) 2 mM. 

c) 4 mM. 

d) 1000 mM.

B) What is the total amount of enzyme?