GALACTOSEMIA

Galactose in Haworth Projection

Presented by: Cherry Kristine Gomez Lavador

BS Biology

IntroductionGalactose is a C-4 epimer of glucose. It is found

in dairy products, sugar beets, and other gums and mucilages. It is also synthesized by the body, where it forms part of glycolipids and glycoprotein in several tissues.

Galactosemia is a rare disorder that affect the body ability to breakdown a food sugar called galactose.

Galactosemia is an autosomal recessive disorder caused by deficient or absent activities of one of the three enzymes involved in the galactose metabolic pathway: galactokinase, galactose-1- phosphate uridyltransferase and UDP-galactose 4’-epimerase.

Historical BackgroundThe first case in literature of the condition that we know

to be galactosemia was reported by Von Reuss, in 1908.However, the first detailed description of classic

galactosemia was given by Goppert in 1917.The causes of classical galactosemia were identified only

some years later, in 1956, by a group led by Herman Kalckar.

Mason and Turner (1935) were the first to report the successful use of a milk-free diet in an infant with galactosemia.

In the 1950s, different strategies to feed infants diet without galactose were discussed in the literature.

Physiological Mechanism About one in every 50,000 babies in the United States is

born with galactosemia.The clinical manifestations of each enzyme deficiency

differ, inpatients with GALK deficiency (Type II Galactosemia) have the mildest clinical consequences as they may present only with cataracts, GALT-deficiency (Type I Galactosemia)potentially lethal and demonstrates long-term, organ-specific complications.

This is how the galactosemia happen when there is no GALT that would binds to the galactose which facilitate the conversion of galactose to glucose.

In A, it show the natural pathway of converting the galactose to glucose, while in B, the Galactose-1-phosphate uridyltransferase and UDP-glucose pyrophosphorylase was deleted and cannot perform its activity in converting the galactose to glucose.

Genetic TransmissionGalactosemia is an inherited autosomal-recessive disorder

of galactose metabolism. People with galactosemia cannot tolerate any form of

milk. The sugar lactose (a disaccharide present in milk) is made

up of equal parts of glucose and galactose; thus a deficiency of the enzymes involved in galactose metabolism can lead to severe clinical consequences.

This show how the galactosemia could be inherited from the parents who are both carrier of recessive gene of galactosemia.

The classical and most severe form is caused by a deficiency of the enzyme galactose-1-phosphate uridyl transferase (GALT).

The gene for galactose-1-phosphate uridylyltransferase ( GALT gene ) is located on the short arm of chromosome 9, in the region 9p13. 

Galactose-1-phosphate uridylyltransferase ( GALT ) is an enzyme responsible for converting ingested galactose to glucose. This enzyme has been shown to belong to the histidine triad family.

Preventive MeasureSigns and Symptoms

Early symptoms may include:Jaundice(yellowing) of the skin and whites of

the eyesVomitingPoor weight gainLow blood sugar (hypoglycemia)Feeding difficultiesIrritabilityLethargyConvulsions

Later signs and symptoms may include:Opaque lenses of the eyes ( Cataract )Enlarged liver, enlarged spleenMental retardationSepsis caused by a specific bacteria ( Escherichia coli )Cirrhosis liver failureKidney problemsSwelling of the extremities or stomach

Long-term complications include:Poor growthLearning disabilitiesSpeech and language problemsFine and gross motor skill delaysOvarian failure (in girls)Cataracts (usually regress with dietary treatment, leaving no residual

visual impairment)Decreased bone mineral density

Major Organs Affected by Galactosemia

Diagnosis Prenatal Testing

A doctor can determine during a woman’s pregnancy whether her baby has galactosemia through:

a. amniocentesis

b. chronic villus sampling or CVSNewBorn Screening

-Babies are tested for Galactosemia at birth using a tiny blood sample taken from the baby’s heel, the test for low level of the GALT enzyme.

Amniocentesis NewBorn Screening

TreatmentNo treatment or cannot be cure but with

maturation most children develop another enzyme capable of metabolizing galactose. As a consequence, they are able to tolerate galactose as they mature.

Dietary restriction, avoid food and drinks containing galactose like milk, cheese, legumes (dried beans), fermented soy products, organ meat and hydrolyzed proteins.

Conclusion

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