1. What enzymes are regulated?
Enzymes at control points in metabolism
Generally the committed step (not necessarily the first step)
Note that these are usually essentially irreversible steps

6. Aspartate transcarbamylse
3 catalytic clusters (blue and purple) and 3 regulatory clusters (red and yellow)
Lehninger 8-24
6 catalytic monomers
6 regulatory monomers

8. Aspartate transcarbamylase proves the allosteric concept
6 catalytic monomers
6 regulatory monomers

14. Serine proteases
Several different families - all have Ser in active site and all have the same reaction mechanism.
The two most commonly-studied are:
Trypsin family
Subtilisin family

15. Proteases
Proteases of different families break peptide bonds by different mechanisms:
metalloproteinases* (carboxypeptidase A)
serine proteases*
cysteine proteases
aspartyl proteases

16. Trypsin family of Serine Proteases
Includes:
trypsin
chymotrypsin (used for numbering)
elastase
thrombin
coagulation enzymes
plasmin
complement C1r and C1s

17. Zymogen activation (Lehninger 8-31)

18. Chymotrypsin structure (Lehninger Fig 8-18)

19. Specificity pocket explains protease specificity (residues 189, 216 and 226)
Chymotrypsin Trypsin Elastase
aromatic basic small, uncharged
Diagram from Branden & Tooze, 1991