Question

2) (5 marks) The enzyme Happyase follows simple Michaelis – Menten Kinetics

a. The Km of Happyase for its substrate ICE is Km^s = 1mM. Happyase also acts on substrate CREAM and its Km^T =10mM. Is ICE or CREAM the preferred substrate for Happyase? Explain

b. The rate constant k2 with substrate ICE is 2x10^4sec^ -1; with substrate CREAM, k2=4x10^5sec ^-1.  Does Happyase use substrate ICE or substrate CREAM with greater catalytic efficiency? Show calculations and explain your answer

Answer 1

2. a.

The ICE is the preferred substrate for the happynase enzyme. THis is because , its Km^s constant is lower which is only 1mM. That means the reaction rate has reached it's half maximum when the substrate concentration is just 1mM. Where as with the CREAM reaction rate reached its half maximum when the substrate concentration is 10mM. This shows that the enzyme happynase has more affinity to ICE than to CREAM.

b.

Rate constant or k is the rate of an enzymatic reaction. The rate constant of the CREAM reaction is higher than that of the ICE reaction.

Catalytic efficiency is caliculated as the ratio of kcat/Km.

Kcat is the turnover number. Which means the number of product molecules formed in the presence of the enzyme per unit time.

The turnover number for the ICE ( k1) is 2 x 10^4/sec. The Km^S of the ICE is 1mM. The catalytic efficiency is :

2 x 10^4 ^sec-1 / 1 mM = 2 x 10^4/mM sec

Kcat for the CREAM is ( k2) 4x10^5/sec. The Km^T constant is 10mM. The catalytic efficiency is :

4 x 10^5^sec-1 / 10mM = 4 x 10^4 / mM sec.

The catalytic efficiency of CEAM is higher than the ICE. So, it uses CREAM with greater efficiency.