SBK 3013

PRINCIPLE IN BIOCHEMISTRY

GROUP MEMBERS:

AZIREN SANTHARAN (D20091035141)

TUAN ZAKIAH TUAN MAHMOOD

(D20091035112)

NOR FAZILAH ZAINUL (D20091035128)

NURUL IZZATI MUSA (D20091035121)

GALACTOSEMIA

Galactosemia is a

recessive autosomal

genetic disease.

It is the hereditary

condition caused by

the lack of liver

enzyme that is

required to metabolize

GALACTOSE.

• Galactose is metabolize by a couple of enzyme in galactose pathway .

• One enzyme in the pathway is GALACTOSE-1-PHOSEPHATE URIDYLYLTRANSFERASE (GALT).

• The GALT gene is located on chromosome 9 at position 13.

• However, mutations can change the amino acid sequence of the GALT enzyme which prevent the enzyme from being able to catalyze the normal enzymatic reaction.

People with Galactosemia have a mutation in the chromosome 9 that encode for the production

of enzyme GALT.

Lactose is the main type of sugar found in milk and milk

products. It is made of one molecule of galactose and one molecule of glucose.

During digestion, lactose is broken down to galactose

and glucose.

Galactose is further changed by the body into glucose so it

can be used as energy.

Galactosemia occurs when an enzyme, called galactose-1-phosphate

uridylyltransferase’ (GALT) is either missing or not working properly.

This enzyme change galactose into glucose.

When the GALT enzyme is missing or not working properly, galactose cannot

be changed to glucose.

Galactose builds up in the blood in large amounts.

Excess galactose will affect many parts of the body and, over time, may be life-

threatening.

NORMAL

GALACTOSEMIA

GALACTOSE PATHWAY. Normal reaction :

UDP-glucose + galactose-1-phosphate → glucose-1-phosphate + UDP-galactose In this reaction GALT transfer the uridine monophosphate from the glucose to galactose.

If gene is mutated:

Galactose-1-phosphate ACCUMULATE and is converted to galactitol. The accumulating galactose-1-phosphate also acts as a COMPETITOR on

UDP-glucose-phosphorylase (which catalyzes the reaction UTP + glucose-1-phosphate → UDP-glucose) so that UDP-glucose is not produced.

UDP-glucose is needed in combination with galactose-1-phosphate to produce glucose-1-phosphate.

Galactokinase

Galactose-1-phosphate

uridyltransferase

UDP-galactose-4-epimerase

UDP-glucose pyrphosphorylase

SYMPTOMS OF

GALACTOSEMIA

Vomitting.

Poor feeding

(baby refuse to drink milk containing formula).

Poor weight gain.

Exhausted

If a galactosemic infant is given milk, the unmetabolized milk sugar will build up and cause :