Lecture_14legge - Regulation of Enzymatic Activity There are two general ways to control enzymatic activity Enzyme Catalysis 1 Control the amount

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1 Enzyme Catalysis 10/08/2009 Regulation of Enzymatic Activity There are two general ways to control enzymatic activity. 1. Control the amount or availability of the enzyme. 2. Control or regulate the enzymes catalytic activity. Each topic can be subdivided into many different categories. Enzyme amounts in a cell depend upon the rate in which it is synthesized and the rate it is degraded. Synthesis rates can be transcriptionally or translationally controlled. Degradation rates of proteins are also controlled. However, We will be focusing on the regulation of enzymatic activity. Aspartate Transcarbamoylase: the first step in pyrimidine biosynthesis. C O NH 2 OPO 3 -- CH 2 C C H O O - CH 2 C C H O O - COO - N C O NH 2 + + ATCase H 2 PO 4 - COO - H 3 N + H Carbamoyl Aspartate N-Carbamoyl aspartate phosphate This enzyme is controlled by Allosteric regulation and Feedback inhibition Notice the S shaped curve (pink) cooperative binding of aspartate Positively homotropic cooperative binding Hetertropically inhibited by CTP Hetertropically activated by ATP Feedback inhibition Where the product of a metabolic pathway inhibits is own synthesis at the beginning or first committed step in the pathway CTP is the product of this pathway and it is also a precursor for the synthesis of DNA and RNA (nucleic acids). The rapid synthesis of DNA and/or RNA depletes the CTP pool in the cell, causing CTP to be released from ATCase and increasing its activity. When the activity of ATCase is greater than the need for CTP, CTP concentrations rise rapidly and rebinds to the enzyme to inhibit the activity. ATP activates ATCase. Purines and Pyrimidines are needed in equal amounts. When ATP concentrations are greater than CTP, ATP binds to ATCase activating the enzyme until
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This note was uploaded on 02/22/2011 for the course BCHS 3304 taught by Professor Johnson during the Spring '08 term at University of Houston.

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Lecture_14legge - Regulation of Enzymatic Activity There are two general ways to control enzymatic activity Enzyme Catalysis 1 Control the amount

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