regulation

regulation - "#$&""/0/1 2&/$"304...

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Unformatted text preview: !"#$%&" (() *"+%,-./0 /1 2&/$"304 5"6 7/0#"8$4 • Amounts of many key enzymes are regulated at the level of control of transcription, mRNA processing, and/or translation or destruction (proteolytic degradation) of old/unwanted enzymes. • Activities of many key enzymes are regulated in cells, based on metabolic needs/conditions in vivo. • Regulation of enzyme activity can increase or decrease substrate binding afFnity and/or kcat. • 5 ways to regulate protein activity (including enzyme activity): – allosteric control – multiple forms of enzymes (isozymes) – reversible covalent modiFcation – interaction with regulatory proteins – irreversible covalent modiFcation, including proteolytic activation 5"6 7/0#"8$4 • Allosteric control – conformational changes • 2 conformations in equilibrium, "R" (more active) & "T" (less active) – allosteric activators (positive effectors/modulators) – allosteric inhibitors (negative effectors/modulators) • often feedback inhibitors (product of pathway inhibits Frst committed step in pathway) – allosterically regulated enzymes always multi-subunit – Aspartate transcarbamoylase (ATCase) as an example • homotropic effector = activator (substrate aspartate) • heterotropic effectors (activator = ATP; inhibitor = CTP) 5"6 7/0#"8$4 • Activities of many key enzymes are regulated in cells, based on metabolic needs/conditions in vivo. • Regulation of enzyme activity can increase or decrease substrate binding afFnity and/or kcat. • 5 ways to regulate protein activity (including enzyme activity): – multiple forms of enzymes (isozymes) • Different kinetic parameters like Km, and/or different allosteric regulation, with physiological consequences – reversible covalent modiFcation -- example: • phosphorylation/dephosphorylation – interaction with regulatory proteins – examples: • protein kinase A (PKA) – irreversible covalent modiFcation, including proteolytic activation (zymogen activation) • examples: – digestive proteases like chymotrypsin and trypsin – blood clotting cascade !"-&030+ 9:;"#.<"4 • Terminology (some are review): quaternary structure, multimeric protein, ligand, binding site, feedback inhibition, cooperativity, cooperative binding, allosteric, homotropic effector/regulator, heterotropic effector/regulator, allosteric activator (positive heterotropic effector/regulator), allosteric inhibitor (negative heterotropic effector/regulator) • DeFne feedback inhibition and describe how ATCase uses it as a regulatory mechanism • Brie¡y explain the allosteric regulation of ATCase, including its quaternary structure, its role in metabolism, and how its activity is regulated by allosteric inhibition and activation. Include the physiological rationale for the inhibition and activation....
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This note was uploaded on 05/06/2010 for the course BIOC 460 taught by Professor Ziegler during the Spring '07 term at Arizona.

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regulation - "#$&""/0/1 2&/$"304...

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