Proteases (Ser proteases, Thr proteases, Cys proteases)

Question 1

Compare Cys and Ser proteases

Answer 1

-Cys has lower pKa than Ser
-S (in Cys) less electronegative then O (in Ser)

-Cys more easily deprotonated

Question 2

How does bortezomib inhibit Thr peptidase?

Answer 2

-boron covalently binds to enzyme (boron changes from sp2 to sp3)
-mimics alkoxide intermediate - O/OH in same position, etc