Phenylโmethaneโsulfonylโfluoride (PMSF) inactivates serine proteases by binding covalently to the catalytic serine residue at the active site; this enzymeโinhibitor bond is not cleaved by the enzyme. This is an example of what kind of inhibition?
A. Non-competitive
B. Competitive
C. Irreversible
D. pH inhibition
E. Mixed