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Topic: Fructose and Galactose Production  (Read 4978 times)

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Offline constant thinker

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Fructose and Galactose Production
« on: November 27, 2006, 10:01:28 PM »
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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Offline Yggdrasil

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Re: Fructose and Galactose Production
« Reply #1 on: November 28, 2006, 01:36:08 AM »
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.

Offline constant thinker

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Re: Fructose and Galactose Production
« Reply #2 on: November 28, 2006, 09:43:10 PM »
Thank you Yggdrasil.
"The nine most terrifying words in the English language are, 'I'm from the government and I'm here to help.' " -Ronald Reagan

"I'm for anything that gets you through the night, be it prayer, tranquilizers, or a bottle of Jack Daniels." -Frank Sinatra

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