Zbornik - Društvo genetičara Srbije

V-Pos-2 ZBORNIK ABSTRAKATA III KONGRESA GENETIÈARA SRBIJE 205
Subotica, 30. novembar - 4. decembar 2004.
THE IMPOIRTANCE OF ENZYMATIC ANALYSIS IN THE CELLS FOR
DETERMINATION OF SPECIFIC TYPES OF MUCOPOLYSACCHARIDOSES
J. Durkoviæ 1 , I. Kremensky 2 and I. Sinigerska 2
1
Health Center Subotica, Department of Medical Genetics, Subotica
2
Laboratory of Molecular Pathology, University Hospital, Sofia, Bulgaria
Mucopolysaccharidoses are recessive very heterogenic group of diseases caused by
storages in lysosomes. The substances stored are partially degraded mucopolysaccharides.
Degradation of acid mucopolysaccharides begins by separation of glucoseaminoglycans
(GAG) from the proteins. Due to the inherited defectiveness of specific
lysosomal hydrolase enzymes, incompletely hydrolyzed molecules are accumulated in
tissues and they are increasingly excreted in urine. The detection of urinary GAG excess
is the first step in diagnostic work-up of a patient with such clinical features. In case the
increased excretion of GAG is confirmed, examination directed to discriminate the types
of the disease is necessary and that is very important in terms of prognostics and further
treatment of the diseased.
In our case report clinically suspected mucopolysaccharidosis called for metabolic
screening of first morning urine and the positive toluidine blue test result indicated the increased
excretion of mucopolysaccharides. The electrophoretical fractionation of excreted
GAG showed, that heparan sulphate was the predominant component. One dimensional
barium acetate electrophoresis is more suitable than thin layer chromatography for
separation of heparan sulphate. Blood sample was tested for specific enzyme deficiency
in white blood cells. Since the enzyme analysis indicated deficiency of heparin
sulphamidase, MPS III the A type was diagnosed. This enzyme is a specific hydrolase involved
in separating sulphate bonds from amino groups of glucosamines. Heparin
sulfamidase enzyme activities of patient with MPS IIIA in leukocytes is 0,38 nmol/17
h/mg and control subjects is 1,8-6,8 nmol/17 h/mg.
The gene for this enzymes has not been cloned yet. Mucopolysaccharidoses are of special
genetic interest since they show mutation in various loci as well as more than one mutation
in one single locus. Multiple alleles give a similar phenotype but different enzyme
deficiency that results in different products of hydrolysis. This means that DNA diagnosis
(PCR) is made more difficult and therefore making diagnosis of mucopolysaccharidosis
is based on enzyme analyses.