Hexose Phosphate Shunt and Hexose Metabolism Flashcards
What is the first step in the fructose catabolism pathway?
What enzyme does this?
ATP dependent?
Any bi-products?
fructose to fruc-1-p by fructokinase using ATP hydrolysis
no bi-products
What happens to fructose-1-p?
What enzyme does this?
ATP dependent?
Any bi-products?
converted to glyceraldehyde by aldolase B
no ATP
***bi-product: DHAP
What happens to glyceraldehyde?
What enzyme does this?
ATP dependent?
converted to glyceraldehyde-3-p by triose kinase using ATP hydrolysis
How many ATPs are consumed in the fructose pathway?
2
Where does fructose metabolism primarily occur?
liver (and to some extent in the kidney)
What are the isozymes of aldolase and where are they found?
Which ones act of fructose-1-p?
a- muscle
b- liver
c- brain
only B will recognize and act on fructose-1-p
Which aldolase isozymes can act on fructose-1,6-bisphosphate?
a and b (muscle and liver)
The pathway to synthesize fructose from glucose is called what?
polyol pathway
What are the steps of the polyol pathway?
1) D-glucose to sobitol using aldolase reductase (using NADPH using giving off NADP+ and H)
2) sorbitol to D-fructose using sorbital dehydrogenase (using NAD+ and making NADH)
Where is the polyol pathway commonly found?
sperm
What is essential fructosuria?
fructokinase deficiency, inherited
benign disease
How could fructose directly enter glycolysis?
by phosphorylation by hexokinase to fru-6-p
What is hereditary fructose intolerance?
defect in aldolase B in liver
accumulation of fru-1-p is toxic
causes hypoglycemia by inhibiting glycolysis (ATP levels) so patients can’t do gluconeogenesis
What are the steps of galactose metabolism?
1) galactose to galactose-1-p by galactokinase (using ATP)
2) galactose-1-p + UDP-glucose to UDP galactose + glc-1-p using galactose-1-p uridylyltransferase
3) UDP-galactose to UDP-glucose using UDP glucose epimerase
4) UDP-glucose recycles
What is the net product of galactose metabolism?
glc-1-p and ADP