BCCB2000 Lecture Notes - Lecture 18: Primaquine, Hexose, Glyceraldehyde
23 Jun 2018
School
Department
Course
Professor
Pentose Phosphate Pathway and NADPH
Dr Steven Bottomley
PPP and Glucose Metabolism:
Where is the Pentose Phosphate Pathway:
-Reaction occur in cytosol of cells
-Major tissues where PPP is active includes:
oAdipose tissue
oMammary gland
oLiver
oTestes
oPlacenta
oAdrenal cortex
oRed blood cells
-Tissue where little PPP activity
oSkeletal muscle
Role of Pentose Phosphate Pathway:
-Provide a way to interconvert 5-carbon and 6-carbon sugars
oDetermines distribution of carbon for information or energy
-Produce NADPH
-Produce 5-carbon sugars for nucleotide synthesis
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oE.g. ATP, RNA, DNA
-Metabolise dietary 5-carbon sugars
Pentose Phosphate Pathway Not one Two:
-Oxidative pathway
oOxidises glucose-6-phosphate to ribose-5-phosphate
oGenerates NADPH
oGlucose-6-phosphate deghydrogenase plays important role in protection
against reactive oxygen species
Produces NADPH required for reducing glutathione
Deficiency of the enzyme has detrimental effects under certain
conditions
-Non-oxidative pathway
oSeries of carbon transfer reactions producing glycolytic intermediates
Reversible link to the glycolytic pathway
Produces intermediates for glycolysis from ribose sugars
oConverts 5-carbon sugar phosphates to hexose phosphate sugars and
vice versa
oNet result is the synthesis of two hexoses (fructose 6-phosphate) and one
triose (glyceraldehyde 3-phosphate) from three pentoses
Reactions of the Pentose Phosphate Pathway:
Control of Pentose Phosphate Pathway:
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-Oxidative pathway
oLevel of NADP+
NADP+/NADPH ratio = 0.014 cf with NAD+/NADH ratio of 700)
Levels of NADP+ needs to increase a lot before this pathway can
proceed
oGlucose-6-phsophate dehydrogenase is the rate limiting step
oIncrease = more electrons needed
-Non-oxidative pathway
oAvailability of substrates
-Both pathways
oFlow of PPP depends on need for NADPH, ribose-5-phsophate, and
ATP
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Major tissues where ppp is active includes: adipose tissue, mammary gland, liver, testes, placenta, adrenal cortex, red blood cells. Tissue where little ppp activity: skeletal muscle. Provide a way to interconvert 5-carbon and 6-carbon sugars: determines distribution of carbon for information or energy. Produce 5-carbon sugars for nucleotide synthesis: e. g. Pentose phosphate pathway not one two: Oxidative pathway: oxidises glucose-6-phosphate to ribose-5-phosphate, generates nadph, glucose-6-phosphate deghydrogenase plays important role in protection against reactive oxygen species. Deficiency of the enzyme has detrimental effects under certain conditions. Non-oxidative pathway: series of carbon transfer reactions producing glycolytic intermediates. Produces intermediates for glycolysis from ribose sugars: converts 5-carbon sugar phosphates to hexose phosphate sugars and vice versa, net result is the synthesis of two hexoses (fructose 6-phosphate) and one triose (glyceraldehyde 3-phosphate) from three pentoses. Nadp+/nadph ratio = 0. 014 cf with nad+/nadh ratio of 700)
