Fructose and Galactose Metabolism

arne1's version from 2015-09-24 22:26


Question Answer
sources of fructosesucrose, fruits/honey, sorbital (via sorbital dehydrogenase)
fructose is absorbed by GLUT-5 facilitated diffusion, insulin independendt
Aldolase B has higher affinity for Fru-1,6 BP (glycolysis) compared to Fru -1P (fructose metabolism)
hypoglycemia is marked bydrowsiness
benign (essential) fructosuriafructokinase deficiency in liver. Fru is not converted to Fru-1-phopshate and excreted in urine. clinitest shows reducing sugar (fructose) that is NOT glucose or galactose
hereditary fructose intolerancedeficiency of Aldolase B in liver. Fru 1-phosphate is not converted to glyceraldehyde and dihydroxyacetone phosphate. Pi is essentially trapped which results in low ATP and inhibition of gluconeogenesis. glycogenolysis is also inhibited and hypoglycemia results. this occurs flollowing sucrose and fructose intake and NOT in the fasting state!!!
a pt with classical galactosemia is deficient inGALT (converts Galactose 1-P to UDP galactose
lactoseglucose and galactose
classical galactosemia presents withsevere hypoglycemia after milk/galactose, jaundice, hepatomegaly. (2nd-3rd wk of life). Also Opacity of lens due to galactitol (formed via aldose reductase), and neurological damage. REducing sugar (galactose) in urine, NOT glucose.
non-classical galactosemiadefect in galactokinase, which converts galactose to galactose 1-phosphate. we have high galactose in blood but no toxic buildup of gal 1-phosphate.