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September 25-ch6 - for the active site • “competitive...

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September 25, 2007 Chapter 6 Metabolic pathways are controlled in several ways o Control of enzyme synthesis regulates availability o Some enzymes are inactive when synthesized and must be “turned on” to be active o Small organic molecules can bind to enzymes and change/inhibit activity (allosteric regulation) Control of enzyme synthesis o Alcohol dehydrogenase (adh) in the liver Amount produced varies among individuals o Phenylalanine hydroxylase Phenylalanine to tyrosine Phenylalanine accumulates and is converted phenylketones Toxic to infants (phenylketonuria) Enzymes synthesized in inactive forms o Enzymes active only under proper conditions o Pepsin and trypsin: digest proteins Released in inactive forms to prevent auto-digestion Pepsin released as inactive pepsinogen Trypsin released in pancreas as trypsiongen Allosteric regulation o Regulator is neither substrate nor the product o Bins to allosteric regulatory site Modifies active site Drugs and Poisons Drugs and poisons often inhibit enzymes by competing with the natural substrate
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Unformatted text preview: for the active site • “competitive inhibition” • Some permanently bind • Why is methanol poisonous o Methanol is an accidental by product of distillation Illegal in most states to distill alcohol without a license o Binds to same site as ethanol in alcohol dehydrogenase o ADH converts methanol to formaldehyde o Formaldehyde pickles the brain, causes blindness, among other things o Treatment: ethanol • Some drugs and poisons binds active site permanently o Acethylcholinesterase Breaks down acetylcholine, a neurotransmitter Ach freese synapses of free acetylcholine In the absence of Ach, muscles, glands, CNS are overstimulated Sarin gas (nerve gas used in warfare) is an acetylcholinesterase Insecticides target the ACh in certain insects • Environmental conditions o Three-dimensional structure of an enzyme is sensitive to pH, salts, temperature ect. o...
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