Question

You are studying a cysteine protease and want to better understand its mechanism and inhibition. What are the likely consequences of mutating the active site cysteine to an alanine and why? What are the likely consequences of mutating the active site cysteine to a serine and why? What considerations should you make when designing a competitive inhibitor for your protease and why?

Answer 1

Cysteine proteases, also known as thiol proteases, are enzymes that degrade proteins.

Mutating the active site cysteine to alanine would result in the inactivation of proteases as there won't be a nucleophile attack as it happens with the nucleophilic cysteine residue in Cysteine proteases.

Serine is the better substitute for enhancing the activity. Serine and Cysteine differ only in the swap of a sulfur atom with oxygen. So, the chain remains the same size and retains its hydrophilic properties. It can act as a better nucleophile as oxygen is more electronegative.

this is how cysteine act: