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Lecture 26 Glycogen Synthesis-BW

Of c h a i n b y 1 4 l i n k a ges mcb 2000 lecture

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Unformatted text preview: b r a n c h i ng e n z y m e and reattachment by -1 , 6 l i n k a g e s . Regulation of Glycogen Synthesis Glycogen synthase Dephosphorylated and active increase blood glucose increase insulin/glucagon ratio dephosphorylate glycogen synthase to stimulate synthesis; also inhibit glycogen degradation THe regulation of glyocgen synthesis - glyocgen degration - becuase glycogen dsynthessi and degration - regulated in opposite way - if you want to synthesis glycogen - the enzyme is dephosphorlated - in the fasted statte the glyocgen s ynthesis is phosphorlated and less active no in the fed state - take off the phosphate that glyagon singalling put on norw syntehsis glycogen - glucose concentation high - ready to go. 4/15/13 MCB 2000 Lecture 26 Regulation of Glycogen Synthesis by Insulin High glucose - trigger insulin - insulin binding to receptor autophosphorlation - inslin receptor IRS-1. the binding kinase. activiate protin kinase that will inactive GS kinase. red means inhibited and blue means active. glyocgen synthase - less active when insulin glcaogen r atio low. phsohporylate glyocgen syntahse -inactive ( fast state) - fed state - turn off the enzyme glyocgen s ynthase kinase that inhbited glyocgen synthase insulin signalling phosphorlation - kinase activated will turn off the enzyme now it becomes inactive - the second thing insulin does - will active a phsophate inactive active active active activate PP1 - enzyme will remove - active phosphate will dephosphyale to mke GS active. insulin actives a kinase which inactive glyocgen 4/15/13 s yntahse kinase - glycogen syntahse will not longer be phosphorlated. MCB 2000 Lecture 26 Insulin signalling activates kinases which will inactivate GS kinase Insulin signalling activates PP1 phosphatase which will dephosphorylate GS, making it active. s econd thing: activate a phosphaase - remove phosphate from any preexcisitng - convenrted to active conformation of glyocgen syntahse - insulin has two apporach - only activated phosphate - any active can be phosphrlated. cycle with no end. c ounter product - have to turn off kinsae and turn on s ynthase. Regulation of Glycogen Synthesis The enzyme, Glycogen synthase, is hormonally regulated Phosphorylated at multiple sites and inactive (by glucagon or epinephrine cascade) in liver, phosphorylated in response to a decrease in the insulin/glucagon ratio (Glucagon GPCR, cAMP, PKA activation); glycogen degradation stimulated by same signalling mechanism. 4/15/13 MCB 2000 Lecture 26 Glycogen Synthesis and Degradation Are Inversely Regulated Fed (Glycogen degradation) 4/15/13 Controled inversely (synthesis and degration) - right hand graphglycogen synthase active - trigger by glucose avilablilty and high insulin:glucagon ratio. insulin signalling - protein phsophate 1 - hs two substrate (glycogen synthase- remove phsophate teh c ordinate regulation - things happenign s ynthase becomes active) when it removes the phosphate from together in a coordinated fashion - dont glycogen phosporlates - that enzyme becoms less active. have to come up with add. enzyme or dephsophorlation in response to insulin signalling has opposing pathways to turn on or off something. effects to glycogen metbaolism. one pathway on and other off. degrade glycogen: the graph on the right will be reverse (synthase would MCB 2000 Lecture 26 decrease and degration would increase) inversely regulated....
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