Fructose

Describe the Oxidation of Fructose ?

2 main routes:

• conversion to fructose 6-P in small intestine

• conversion to fructose 1-P, primarily in liver

What enzyme converts fructose to fructose 6-P ?

hexokinase

What does Aldolase B do ?

Fructose 1-P is split into two 3-carbon molecules

Where is the main site of metabolism of free fructose ?

Liver-Transport Fructose into hepatocytes through GLUT2

Why is fructose metabolism faster than glucose metabolism ?

because it bypasses PFK1, the main rate limiting step in glycolysis

How does glyceraldehyde turn into glycerol3-P ?

Glyceraldehyde is a precursor for glycerol

Due to the lack of regulation in this pathway, high pyruvate levels are formed from fructose. Why is this an issue?

leads to high levels of acetyl CoA

High levels of triglyceride production

So fructose can lead to triglyceride production all on its own increasing lipids in the body

Also increasing the reparatory process

Leading to its association with obesity, diabetes, NAFLD

How is Fructose 6-P can be converted into glucosamine 6-P ?

amine transfer with addition of glutamine

What is the precursor for all nitrogen-containing sugars in the body ?

Glucosamine 6-P

How is fructose metabolized at low levels ?

At low levels it can be metabolized directly via glycolysis following conversion to fructose 6-P in the small intestine

How is fructose metabolized at high levels ?

At high levels (e.g., from sucrose or HFCS) an alternative pathway is followed in the liver that joins the glycolytic pathway at the three-carbon stage