cholesterol biosynthesis

cholesterol biosynthesis - Cholesterol Biosynthesis...

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Cholesterol Biosynthesis Cholesterol Biosynthesis Uses of Cholesterol (Review) Membranes, crucial component Precursor for bile acids, solubilizes lipids      in intestines Precursor to steroid hormones Precursor to vitamin D                       *Synthesis mostly in liver* *Synthesis mostly in liver*
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Cholesterol Biosynthesis-Overview Cholesterol Biosynthesis-Overview          a           a '              b            b             b 3C          C 6           C' 6           C 5             C 10             C 15            C 30             cholesterol a. HMG-CoA synthase is common to sterol and ketone body synthesis a ' . HMG-CoA reductase makes  mevalonate (MVA), the key and first  intermediate of sterol biosynthesis. This is a highly regulated step. b.  An “ active isoprene ” is made which  may combine with another C unit to
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3C          C 6           C' 6           C 5             C 10                     c              d C 15            C 30             cholesterol c. Two C 15  units dimerize to form  squalene , a C 30  molecule. d. Squalene is cyclized using O 2  and many enzymes  to give  cholesterol --The whole process is very energy dependent in terms of  ATP and NADPH utilization--
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Mevalonate Pathway for Cholesterol Biosynthesis
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Mevalonate is synthesized via  Mevalonate is synthesized via  HMG-CoA synthase   HMG-CoA synthase   3C2 →C6 1. Condensation of two acetyl-CoA 2. Add another acetyl from acetyl- CoA  3. Beta-hydroxy-beta methylglutaryl-CoA reductase (HMG-CoA reductase) makes mevalonate; regulation step of cholesterol  synthesis  Lehn fig 21-34
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Three kinases and    a  decarboxylase X 3 X 3 Lehn fig 21-35 isoprene Isoprene is made from Isoprene is made from                     mevalonate mevalonate                       C6 C6   C5    C5  needed to produce 2 activated isoprene molecules 
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2 isoprene units join head-to-tail to form  geranyl pyrophosphate (C10)   pyrophosphate hydrolysis drives rxn.    another  isoprene is added head to tail to form farnesyl pyrophosphate (C15)
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This note was uploaded on 09/18/2011 for the course BCH 4024 taught by Professor Allison during the Spring '08 term at University of Florida.

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cholesterol biosynthesis - Cholesterol Biosynthesis...

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