Cheet heet biochem for exam 2

Cheet heet biochem for exam 2 - Unbound enzyme=[Et[ES Rate...

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2. 3. 1.equil. Disa.constant.2. frac. Occ. Bind. Sites.3.ppO2.5 e’of’ES’formation’=’ k 1 ([E t ]’−’[ES])[S]’ ’ e’of’ES’breakdown’=’ k −1 [ES]’+’ k 2 [ES]’ rate equation for a 1substrate lyzed reaction. Km=(k2+k-1)/k1 uncomp m oduct release happens to be rate limiting in this case. At saturation the en ax = k 3 [E t t is used to describe the limiting rate of any enzyme catalyzed reaction at Hemoglobin A tetramer of two a-chains (141 amino acids each) and two b- chains (153 amino acids each); a2b2 - Each chain has 1 heme group; hemoglobin can bind up to 4 molecules of O 2 - Binding of O exhibited by positive cooperativity - transport’oxygen - The’structure’of ’ oxygenated’Hb’different’frm unoxygenated’Hb - CO,’H + ,’CO2,’Cl - ,’ and’2,3 -bisphosphoglycerate’(BPG)’ affect’the’ability’of’Hb’to’bind’and’ transport’oxygen -structural’changes’ after’binding -allosteric -less’room’in’ oxy -T>R’stability(opp’for’deoxy),’ O’ makes’T ->R., ’ -Conformational’change from’the’T’state’to’the’R’s tate’involve breaking’ion’pairs’between’the’a1 -b2 interface ’ –B1-His’to’asp,a2lys’to’b1’ coo,’a1arg ->a2asp’and’a2asp’to’a1’arg.’ - The’transition’from’the’T’state’to’the’ R’state’shifts’the’subunit’pairs’ substantially,’affecting’certain’ion’ pairs -’ Myoglobin Distal histidine binds to O2. Proximal his -forms coord. Covalent bond with heme. - Need to store oxygen for metabolism. Protein side- chains lack affinity for O 2 Some transition metals bind O 2 well but would generate free radicals if free in solution Organometallic compounds such as heme are more suitable but Fe 2+ in free heme could be oxidized to Fe 3+ if two heme molecules share an oxygen molecule Solution: Capture the oxygen molecule with heme that is sequestered inside the proteinIn mammals, myoglobin is the main oxygen storage protein. A single polypeptide chain of 153 amino acids A single heme group in a hydrophobic pocket 8 regions of a-helix; no regions of b-sheet Most polar side chains are on the surface Nonpolar side chains are folded to the interior. Two His side chains are in the interior, involved with interaction with the heme group Fe(II) of heme has 6 coordinates sites; 4 interact with N atoms of heme, 1 with N of a His side chain, and 1 with either an O 2 molecule or an N of the second His side chain If’n=1’there’is’nocooperativity The’upper’limit’is,’the’number’of’binding’sites.’In’hemoglobin ’ could’reach’4’in’theory.
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Cheet heet biochem for exam 2 - Unbound enzyme=[Et[ES Rate...

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