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Unformatted text preview: 1 Chem 476 HW 8 Due Nov 2, 2007 “Catalytic Strategies” Name:________________________ Please complete all questions. Do your work on additional sheets of paper and staple to the back of this sheet. Do not put your answers on this page. You may work with your classmates on this and all homework assignments. I will grade the same three questions for all students and post the answers to the questions after they are due. I.) Problems from the textbook and supplement (do not hand in). Answers are in the textbook (short answers) and supplement (full answers to text AND supplement), but work through on your own first. : Text: 9.1-13 (Most are short answer) Supp: 9.1, 2, 4-6, 9, 10, 15 II.) Additional Problems to hand in : 1.) (a) Sketch an S1 pocket that might cleave a peptide specifically after acidic residues. (b) after alanine and glycine. a.) The pocket shown here has lysine at the base which would have a favorable electrostatic interaction with an acidic residue. b)The pocket shown here is based on elastase, in which I added a few (1-2) more R groups (Fig 9.13). Elastase cleaves after alanine and serine. By adding a little more steric bulk to the S1 pocket, all but the smallest amino acids will be sterically excluded. R R NH 3 + 2 2.) Offer two explanations as to why the catalytic triad triple mutant in Figure 9.16 still reacts 1000-fold faster than the uncatalyzed reaction. Your answer should be explained at the molecular level. The triple mutant can still bind substrate and orient it for water attack (strategy of approximation). Note that covalent catalysis can no longer be possible since the serine has been removed. The mechanism must involve direct attack by water, as in the aspartyl and metalloproteases. Also, appears that the oxyanion hole is still intact....
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This note was uploaded on 07/23/2008 for the course CHEM 476 taught by Professor Bevilacqua,philip during the Fall '07 term at Pennsylvania State University, University Park.
- Fall '07