Chemical Forums
Specialty Chemistry Forums => Biochemistry and Chemical Biology Forum => Topic started by: constant thinker on November 27, 2006, 10:01:28 PM
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This is a random question I was thinking about...
What causes fructose and galactose to be produced instead of glucose?
Mainly I just want to know what is going on for those 2 sugars to be produced. There must be a difference compared to glucose production to cause the different isomers. I know it can't just be a random occurrence here and there when you consider that sugar is sucrose, and milk has lactose.
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In humans, both fructose and galactose can be obtained from diet. They can also be synthesized from glucose. The enzyme UDP-Gal-4-epimerase can convert a nucleoside-activated glucose (UDP-Glc) to UDP-Gal. The epimerase works by oxidizing the equatorial OH on carbon 4 to a ketone, then stereospecifically reducing the ketone to a hydroxyl in the axial position.
Fructose is made from glucose in glycolysis. The enzyme, glucophosphate isomerase converts glucose-6-phosphate to fructose-6-phosphate. Here, the reaction proceeds through an enol intermediate.
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Thank you Yggdrasil.