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UKCD Biochem Lec 9
Terms from Biochem lecture 9
| Question | Answer |
|---|---|
| Regulatory Strategies | Allosteric control - binding substrate causes conformational control, activator or inhibitor, Multiple forms of enzymes, Reversible covalent modification, Proteolytic activation |
| ATCase | Allosteric Regulation, ATCase catalyzes the first step in pyrimidine synthesis. 6 regulatory subunits and 6 catalytic subunits, Tetrahedral transition state likely |
| CTP | inhibits ATCase, structurally different from the substrates, CTP must bind to a different site in ATCase |
| PALA | is a potent inhibitor of ATCase and binds very tightly |
| T state | inactive |
| R state | active |
| concerted transition | the conformational change is “all or none” |
| concerted mechanism | binding of substrate induces all subunits to adopt the R state, binding CTP pushes all subunits towards the T state |
| sequential mechanism | there are intermediate states in which some subunits are in the T state and some are in the R state, negative cooperativity |
| homotropic | undergoes substrate-induced allosteric interactions |
| heterotropic | ATP/CTP-induced allosteric interactions |
| Hemoglobin | is made up of four subunits - 2 α-subunits and 2 β-subunits, oxygen-bindingcapacity is due to a prosthetic group bound by each subunit - the heme, Four oxygens can be bound - one per subunit |
| cooperative binding | Binding one oxygen pushes the interface towards the R state, making it easier to bind a second, and so on |
| Bohr effect | H+ and CO2 promote hemoglobin release of oxygen |
| carbamates | CO2 reacts with the terminal amino groups |
| Isozymes | enzymes differ sequence catalyze same reaction, coded separate genes via gene duplication/divergence, display diff kinetic behavior, diff substrate affinities, or regulated in different manners, fine-tuning of processes by using different amounts of each |
| Covalent Modification | attachment of a molecule to an enzyme (or other protein) can alter its activity, reversible or irreversible |
| Protein kinases | catalyze addition of phosphoryl group |
| multifunctional kinases | they phosphorylate many different targets |
| Dedicated kinases | phosphorylate a single protein or family of closely related proteins |
| Protein phosphatases | catalyze removal of phosphoryl group |
| PKA | phosphorylates specific serines and threonines, activated by cAMP, two kinds of subunit: two large regulatory subunits (R) and two smaller catalytic subunits © |
| pseudosubstrate sequence | look like the real sequence |
| zymogens | inactive precursors, activated by proteolytic cleavage occur outside cell |
| Cleavage of a specific peptide bond | activates the enzyme |
| Trypsin | enteropeptidase, is the common activator of all the pancreatic zymogens |
| Oxyanion hole | stabilizes the tetrahedral transition state |
| specific protease inhibitors | Need different mechanism to turn off proteolytic enzymes |
| Blood clots are formed by a series of zymogen activations | a cascade: leads to large amplification |
| Intrinsic pathway | results from rupture of blood vessels |
| Extrinsic pathway | results from tissues releasing clotting substances in response to trauma |
| serpins | serine protease inhibitor, antithrombin III, plasmin |
| Heparin | increases the rate of formation of complexes of antithrombin with the clotting serine proteases – anticoagulant |
| Plasmin | formed by proteolytic activation of plasminogen, an inactive precursor. This is carried out by tissue-type plasminogen activator (TPA), another serine protease |
| Trypsin cleaves | peptide bond |
| π-chymotrypsin cleaves | other π-chymotrypsin molecules to form α-chymotrypsin. |
| The three chains of α-chymotrypsin are connected by | two disulfide bonds |
Created by:
wiechartm
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