Week 4 - Galactose Pathway

Question 1

Galactose

Where does galactose metabolism occur?

How can it be produced?

Answer 1

glucose isomer

metabolism occurs mainly in LIver*

Lactose is cleaved by lactase to produce galactose and glucose

Question 2

Primary Lactase deficiancy..

Answer 2

Lactase deficiency results in flatulance and diarrhea when dietary sugars are consumed.

Primary lactase deficiency is an autosomal recessive condition in which lactase activity declines over many years, usually beginning in adolescence.

Question 3

Secondary lactase deficiendcy

Answer 3

Secondary lactase deficiency is due to damage of brush border of intestinal enterocytes due to intestinal disease. Radiation or infectoin can cause this

Question 4

Congenital lactase deficiency

Answer 4

Congenital lactase deficiency, a very rare genetic condition, is the complete absence of lactase

Question 5

What heppens when lactase does not function properly?

What are the end products of galactate metabolism?

Answer 5

If lactase isn’t functioning properly pts cant get galactose into cells…Inhibiting metabolism

The end product of galactose metabolism is glucose 1-phosphate. The glucose 1-phosphate can enter glycogenesis directly, or be converted to glucose 6-phosphate for glycolysis or export (remember this can only happen in liver cells, the export part)

Question 6

Enzyme epimerase

Answer 6

Catalyzes reaction between UDP galactose and UDP glucose

Question 7

Galactosemia non classical vs classical

Answer 7

Non-classical galactosemia is a deficiency in galactokinase

Classical galactosemia is a deficiency in the enzyme galactose 1 phosphate uridylyltransferase

Question 8

Glactokinase deficiency

Answer 8

Galactose builds up because enzyme galactokinase (to phosphorylate galactose) isnt functioning.

Enzymes that make sorbitol and glucose can also act on galactose… (in the eye, polylol pathway)

it is similar to diebetes.. galactos increases.. can accumlate in eye and cause cataracts and lens protein glycosylation

Treatment - eliminate galactose from diet

Good prognosis

Question 9

Galactose 1-phosphate uridyl transeferase deficiency

Answer 9

“classical galactosemia”; autosomal recessive; very serious

early onset (1-2 weeks old) jaundice, hepatomegaly, hypoglycemia, lethargy, FTT

treatment: eliminate galactose from diet;

prognosis is poor

**This traps galactose 1 phosphate in liver, also using and trapping all of the phosphate in liver… Other liver functions rely on this phosphate.

Question 10

Epimirase deficiency

Answer 10

Benign form… only affects leukocytes and erythrocytes

Serious all tissues similar to transferase deficiency

tratment is a galactos restricted diet - restricted not galactose free - becuase they cant get UDP galactose otherwise (needed for certain functions, glycokalix)

UDP galactose is a substrate for glycosylation of cells.. makes glycokalix - forms gel around gell to protect it **