Question

The clinical symptoms of two forms of galactosemia show radically different severity.

1. Deficiency of galactokinase
2. Deficiency of UDP-glucose:galactose 1-phosphate uridylyltransferase

Although both types produce gastric discomfort after milk ingestion, deficiency of the transferase also leads to liver, kidney, spleen, and brain dysfunction and eventual death.

Explain, what products accumulate in the blood and tissues with each type of enzyme deficiency? (3 point)

List the symptoms for each type of deficiency. (3 point).

Explain which of these products is more toxic and why?

Answer 1

Answer -

A.. Galactosemia due to deficiency of enzyme galactokinase or Galk deficiency type 2 galactosemia .

Due deficiency of Galk enzyme , Galactose is not phosphorylated into Galactose 1 Phosphate.
There is accumulation of Galactose in blood and tissues.
also the product of reaction Galactose 1 Phosphate becomes deficient .

Accumilated Galactose converted into Galactitol a form of sugar alcohol. Excess build of galactitol in eye lens causes bilateral cataracts. Galactitol is osmolent which imbibes water in lens causing cataracts.
symptom : Cataracts.
This form of galactosemia is relatively mild.

B.Galactosemia due to deficiency of enzyme UDP-glucose:galactose 1-phosphate uridylyltransferase or GALT deficiency type 1galactosemia

Due to Deficiency of GALT enzyme , Galactose 1 phosphate and UDP glucose is not converted into Glucose 1 phosphate and UDP Galactose .

Accumilation of Galactose 1 phosphate in blood and tissue. Galactose 1 phosphate keeps the inorganic phosphate bound to itself leading to deficiency of phosphate in cytoplasm . Stopping or slowing down of essential processses such as ATP synthesis , Glycogen breakdown , Gluconeogenesis,

Galactose 1 phosphate inhibits phospho gluco mutase. essential for glycogen breakdown.

Symptoms: Hypoglycaemia under fasting condition , Bilateral cataract , Jaundice , mental retardation.

This form galactosemia is severe .

Galactose 1 phosphate is more toxic product as it affects multilple metabolic pathways leading to severe conditions while galactose converted to Galactitol affects eye lens giving cataracts .

Both galactosemia are autosomal recessive in heredity mechanism.