engleski

Kinetics and activity of arylsulfatase A in leukocytes derived from patients with cerebral palsy

Arylsulfatase A (ASA, EC 3.1.6.1) is a lysosomal enzyme involved in sulfatide catabolism. Deficiency of ASA causes metachromatic leukodystrophy, rare autosomal recessive disorder characterized by the storage of cerebroside sulfate mainly in the nervous tissue. The onset and clinical severity of the disease are related to the type of mutation in ASA gene and consequently to the enzyme deficiency. A large number of mutations and polymorphisms in the ASA gene resulting in different levels of decreased enzyme activity have been reported so far. It has been suggested that such mutations may contribute to pathogenesis of neuropsychiatric disorders. Interestingly, none of detected mutations resides in the catalytic site of the enzyme. Physico-chemical properties of the arylsulfatase A have been extensively studied and its anomalous kinetics in biological samples has been described. The aim of this preliminary study was to determine kinetic properties of arylsulfatase A in leukocytes derived from healthy individuals and patients with diagnosis of spastic cerebral palsy. ASA activity was measured by spectrophotometry (lambda=515 nm) using p-nitrocatechol sulfate (pNCS) as chromogenic substrate. Kinetic parameters of leukocyte arylsulfatase A were determined in dependence of substrate (pNCS) concentrations. Results showed decreased ASA activity in samples derived from patients. Previous findings indicated that changes observed in enzyme activities could not always be explained only as the consequence of mutations in the ASA gene. Other (epigenetic) mechanisms may be responsible for such finding, possibly through different modifications and changes in enzyme structure leading to its inefficiency. Also, the analysis of kinetic properties of the arylsulfatase A may provide additional information and better insight into the mechanism of altered activity of this enzyme in cerebral palsy and several other pathological conditions.

arylsulfatase A; kinetics; specific activity; cerebral palsy

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