Fructose, Galactose, and HMP Shunt

Question 1

Essential fructosuria

Answer 1

defect in fructokinase (takes fructoses to F1P)

autosomal recessive

benign, asymptomatic since fructose does not enter cells, will show up in blood and urine.

-may present as asymptomatic with POSITIVE urine glucose stick, since stick only tests for reducing sugar.

Question 2

Fructose Intolerance

Answer 2

deficiency in aldolase B enzyme (liver)

aldolase B usually cleaves F1P into DHAP and glyceraldehyde. without it F1P will accumulate in cells, causes decrease in phosphate, inhibition of glycogenolysis, gluconeogenesis.

sx: hypoglycemia, jaundice, cirrhosis, vomiting
txt: decrease intake of fructose and sucrose.

Question 3

Galactokinase Deficiency (non-classical galactosemia)

Answer 3

when galactose is ingested, galactitol will accumulate (cataracts in infants)

autosomal recessive, galactose will accumulate in blood and urine

Question 4

Classic Galactosemia

Answer 4

Deficiency in Galactose-1-P Uridylyltransferase.

–build up of toxic substances (including galactitol in eye) that leads to failure to thrive, jaundice, hepatomegaly, mental retardation.

–classically presents with jaundice due to liver’s inability to conjugate bilirubin, and sepsis (ecoli)

Question 5

G6PD deficiency

Answer 5

main enzyme in the oxidative pathway of the HMP shunt, leads to the production of NADPH

–NADPH is important for the reduction of oxidative stress, by reducing glutathione

–especially important in those whose bodies are at increased risk of oxidative damage due ti medications/foods (antimalarials, fava beans, antituberculosis)