Figure: hexose monophosphate shunt

Biochemistry

• source of ribose
• thought to provide reducing equivalents for Cyt P450
• NADPH is generated when glucose is oxidized to ribose-5-phosphate
• the Hexose Monophosphate Shunt also catalyzes the inter-conversion of 3, 4, 5, 6, & 7-carbon sugars in a series of non oxidative reactions
• all of these reactions occur in the cytoplasm

• hexose monophosphate shunt 1
  • enzyme: glucose-6-phosphate dehydrogenase
  • substrate: glucose-6-phosphate + NADP
  • product: 6-phosphogluconolactone + NADPH
• hexose monophosphate shunt 2
  • enzyme: lactonase
  • substrate: 6-phosphogluconolactone + H2O
  • product: 6-phosphogluconate
• hexose monophosphate shunt 3
  • enzyme: 6-phosphogluconate dehydrogenase
  • substrate: 6-phosphogluconate + NADP
  • product: ribulose-5-phosphate + NADPH
• hexose monophosphate shunt 4
  • enzyme: phosphopentose isomerase
  • substrate: ribulose-5-phosphate
  • product: ribose-5-phosphate)
• hexose monophosphate shunt 5
  • enzyme: phosphopentose epimerase
  • substrate: ribulose-5-phosphate
  • product: xylulose-5-phosphate
• hexose monophosphate shunt 6
  • enzyme: transketolase
  • substrate: xylulose-5-phosphate + ribose-5-phosphate
  • product: sedoheptulose-7-phosphate + glyceraldehyde-3-phosphate
• hexose monophosphate shunt 7
  • enzyme: transaldolase
  • substrate: sedoheptulose-7-phosphate + glyceraldehyde-3-phosphate
  • product: fructose-6-phosphate + erythrose-4-phosphate
• hexose monophosphate shunt 8
  • enzyme: transketolase
  • substrate: xylulose-5-phosphate + erythrose-4-phosphate
  • product: fructose-6-phosphate + glyceraldehyde-3-phosphate