Subtilisin (MW = 27,600) is a bacterial protease that can catalyze hydrolysis of certain amino acid esters and amides. For the synthetic substrate N-acetyl-L-tyrosine ethyl ester (Ac-Tyr-OEt), subtilisin exhibits Km and kcat values of 0.15 M and 550 s-1, respectively.

(a) What is the Vmax for the hydrolysis of Ac-Tyr-OEt when the subtilisin concentration is 0.4 mg ml-1?

(b) Indole is a competitive inhibitor of subtilisin with a Ki of 0.05 M. What is the Vmax for Ac-Tyr-OEt hydrolysis by 0.40 mg ml-1 subtilisin in the presence of 6.25 mM indole?

Question

Subtilisin (MW = 27,600) is a bacterial protease that can catalyze hydrolysis of certain amino acid esters and amides.  For the synthetic substrate N-acetyl-L-tyrosine ethyl ester (Ac-Tyr-OEt), subtilisin exhibits Km and kcat values of 0.15 M and 550 s-1, respectively.

(a)  What is the Vmax for the hydrolysis of Ac-Tyr-OEt when the subtilisin concentration is 0.4 mg ml-1?

(b)  Indole is a competitive inhibitor of subtilisin with a Ki of 0.05 M. What is the Vmax for Ac-Tyr-OEt hydrolysis by 0.40 mg ml-1 subtilisin in the presence of 6.25 mM indole?

aaronq · Answer

a) $k_{cat}=\dfrac{V_{max}}{K_m}$

b) it's the same, competitive inhibitors don't affect $V_{max}$