Fructose and Galactose

Question 1

What is Essential Fructosuria?

Answer 1

Deficiency of fructokinase;
Benign condition;
Fructose not taken up by liver cells;
Fructose appears in urine (depending on intake);

Question 2

Function of Fructokinase (liver):

Answer 2

Transform Fructose in Fructose-1-Phosphate;

Question 3

Hereditary Fructose Intolerance - Cause:

Answer 3

Aldolase B deficiency;
Result: depleting ATP on liver;

Question 4

Characteristics of hereditary fructose intolerance:

Answer 4

Baby just weaned from breast milk;
Failure to thrive;
Symptoms after feeding - Hypoglycemia (seizures);
Enlarged liver;
Part of newborn screening panel;

Question 5

Treatment of hereditary fructose intolerance:

Answer 5

Avoide fructose, sucrose and sorbitol

Question 6

Sorbitol can be methabolized by Polyol Pathway into fructose and thats why people with Hereditary Fructose intolerance have to avoid Sorbitol.

Answer 6

True

Question 7

Galactose is commonly found in lactose.

Answer 7

LACTOSE = GLUCOSE + GALACTOSE

TRUE

Question 8

Galactose is converted to Galactose 1- Phosphate by which enzyme?

Answer 8

Galactokinase

Question 9

Galactose-1-Phosphate Uridyltransferase (GALT) transform GALACTOSE 1- PHOSPHATE INTO:

Answer 9

Glucose 1 Phosphate

Question 10

Classic Galactosemia is caused by Deficiency of Galactose 1-phosphate uridyltransferase.

Answer 10

True
This is a Autosomal recessive disorder.

Question 11

As consequency of deficiency of GALT, what happends in Classic Galactosemia?

Answer 11

Galactose 1 phosphate accumulates in cells;
Leads to accumulation of galactitol in cells.

Question 12

Galactose is coverted to Galactitol by which enzyme?

Answer 12

Aldose reductase;

This enzyme also converts Glucose to Sorbitol;

Question 13

Main problems of classic galactosemia:

Answer 13

• Presents in infancy - few days of lofe, after consumtion of milk;
• Liver accumulation galactose/galactitol;
• Liver failure, Jaundice, Hepatomegaly, failure to thrive;
• Cataracts if untreated;

Question 14

Treatment of galactosemia:

Answer 14

Avoid galactose

Question 15

There is a screening for GALT enzyme activity which identify Galactosemia.

Answer 15

TRUE

Question 16

Galactokinase deiciency is a milder form of galactosemia.

Answer 16

True

Question 17

In galactokinase deficiency galactose acumulates in blood and urine.

Answer 17

True

Question 18

What is the main problem of Galactokinase Deficiency?

Answer 18

Cataracts as child/young adult.

Question 19

Sorbitol can be converted to fructose by the enzyme sorbitol dehydrogenase.

Answer 19

TRUE

Question 20

Fructose enters the glycolytic pathway at a point beyond the rate-limiting glycolysis enzyme, phosphofructokinase-1 (PFK1). It is more rapidly metabolized compared with glucose and galactose, which must be metabolized using the enzyme PFK1.

Answer 20

TRUE

Question 21

Among patients with essential fructosuria, a small amount of fructose can be metabolized by the…

Answer 21

glycolytic enzyme hexokinase

Question 22

Classic galactosemia is caused by a deficiency of the enzyme galactose 1-phosphate uridyltransferase (GALT). Children born with this condition cannot metabolize galactose and become ill shortly after consuming breast milk which contains lactose, a disaccharide of glucose and galactose. Symptoms develop because galactose is converted to galactose-1-phosphate which cannot be metabolized into the glycolytic pathway. Galactose-1-phosphate accumulates in cells and depletes the phosphate pool for the formation of ATP. Decreased ATP inhibits glycogen breakdown and gluconeogenesis. This leads to hypoglycemia and liver damage after consumption of galactose.

Answer 22

True

Question 23

How are these tests including plasma galactose, red blood cell galactose-1-phosphate concentration, and blood and urine galactitol levels in Classic Galactosemia?

Answer 23

All of these are increased compared to normal in subjects with classic galactosemia.