Question

Orotic acid is decarboxylated in the absence of a catalyst with a half-time of 78 million years which corresponds to a rate constant of 2.8 × 10^-16/sec. Orotidine-5’-phosphate decarboxylase, an enzyme in the pathway for pyrimidine biosynthesis, carries out the same reaction with a k_cat of 39/sec. The catalytic power of the enzyme is:

		7.2 × 1014
		1.4 × 1017
		2.3 × 103
		3.6 × 1015

Answer 1

Catalytic power or catalytic efficiency is defined as, the ration of rate of catalyzed reaction(Kcat) to the rate of corresponding uncatalyzed reaction (Kuncat)

Mathematical expression thus,

Catalytic power = Kcat / Kuncat

For Orotic acid decarboxylation we have, Kcat = 39 s^-1 and Kuncat = 2.8 x 10^-16 s^-1.

Hence, Catalytic power = 39 / (2.8x10^-16)

Catalytic power = 1.39 x 10¹⁷.

i.e. Catalytic power 1.4 x 10¹⁷.

The catalytic power of enzyme Orotidine-5'-phosphate decarboxylase is 1.4 x 10¹⁷.