General Biochemistry notes set 6
General Biochemistry notes set 6 4115
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This 2 page Class Notes was uploaded by Thomas Salazar on Sunday October 16, 2016. The Class Notes belongs to 4115 at Virginia Polytechnic Institute and State University taught by Dr. Richard Helm in Fall 2016. Since its upload, it has received 12 views. For similar materials see General Biochemistry in Biochemistry at Virginia Polytechnic Institute and State University.
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Date Created: 10/16/16
Note set #6 – week 8 General Biochemistry ENZYME REGULATION Phosphorylation o Kinase: puts P on o Phosphatase: takes P off This modification is either on or off However, phosphorylation cascades (an initial phosphorylation event triggering another and so on,) can produce and modulate many types of cell responses Uncontrolled activity of phosphorylation is indicative of cancer cells Regulatory proteins: block access to the catalytic site of kinases; released by cAMP o Auto-regulation: a “pseudo-substrate sequence” in the kinase acts as its own inhibitor and blocks cat. Site. An activator molecule alters the kinase structure and releases the cat. Site Zymogens: inactive forms of proteases, cleavage at specific sites activates them o Proteases do not inactivate until they are degraded by the cell, must be carefully regulated Acetylation o Modulates enzyme function, some activate, some inhibit Allosteric regulation o Allosteric activator and inhibitors (often used in negative feedback cycles) o If [A] is relatively constant, then activators and inhibitors can drastically change the reaction rate o Symmetry Without substrate, all enzyme subunits are T-state Adding S, all units become R-state Allosteric activators favor R-state, called positive heterotrophic reactors Allosteric inhibitors favor T-state, called negative heterotrophic reactors Conversion of one subunit to R-state favors the addition conversion of other units to R-state, such that once one is R, all other subunits become R as well Glycogen Phosphatase: homodimer; (glycogen) + P nglycigen) n-1+ Glucose-1- phosphate o Has two forms, A and B A: phosphorylated, R-state is much more reactive than R-state of B form B: un-phosphorylated, can be regulated more easily by allosteric regulators, while A is typically unaffected by allosteric AMP upregulates activity ATP downregulates activity o Conversion from form B to A is done by phosphorylase kinase, in a series of phosphorylation cascades. G coupled protein receptors o Membrane associated protein systems, 7 membered receptors Note set #6 – week 8 General Biochemistry o Transfer cellular signal from the outside-in; signal ligands don’t enter the cell o Agonists: increase signal strength; Antagonists: decrease signal strength o Inverse agonists: requires a base signal level, turns off signals.