[Arylsulfatase A--physico-chemical properties and the use of enzyme radioimmunoassay in medical diagnosis]. / Arylosulfataza A--wlasciwosci fizyko-chemiczne i zastosowanie w diagnostyce medycznej.

Arylsulfatase A was isolated from urine and human liver. The enzyme was homogeneous with respect to charge and had high specific activity--64 U/mg and 34 U/mg for arylsulfatase A from urine and liver respectively. The enzyme from urine as well as the liver one contained two nonidentical subunits with molecular weights varying about 5 kDa. Treatment of the enzyme from urine, liver and from placenta with endo-beta-N-acetylglucosaminidase F did not remove all carbohydrate from any subunit even in denaturing conditions. Deglycosylation of the enzyme with this one and other glycosidases under various conditions resulted in a decrease in the apparent molecular weights of subunits only by 1-2 kDa. The difference between molecular weights of subunits did not change upon deglycosylation of arylsulfatase A. The results suggest that the presence of two nonidentical subunits is due to presence of different polypeptides rather than various glycosylation of a single polypeptide chain. Arylsulfatase A from urine was inactivated following reaction with diethyl pyrocarbonate at pH 5.5 or at pH 7.0. This confirmed the presence of histidine essential for its catalytic activity. It was also shown that the enzyme was inactivated with ferrate ion, structural analogue of orthophosphate and strong oxidizing agent. The conditions of inhibition of arylsulfatase A carried out with the use of ferrate as well as catalytic and immunochemical properties of the modified enzyme suggest that ferrate reacted with the active site of arylsulfatase A. The results allow to expect that a reactive histidine is present in enzyme's active site and that this aminoacid is modified with ferrate. A simple, sensitive and specific radioimmunoassay was developed for the determination of arylsulfatase A in human serum and urine. The method allows to measure less than nanogram amounts of the enzyme in human body fluids. The test was used to determine arylsulfatase A in serum specimens of 368 patients with histopathologically confirmed cancer of gastrointestinal tract, breast, lung, central nervous system, kidney and woman genital tract. The highest mean concentration of arylsulfatase A in serum and significantly higher than that in the control group of 96 healthy blood donors was found in the case of groups of lung, kidney and central nervous system cancer. The results indicate that the radioimmunoassay determination of serum level of arylsulfatase A might be helpful in diagnosis of lung and central nervous system cancer. Arylsulfatase A serum level cannot be treated as a valuable indicator in the case of cancer of breast and gastrointestinal tract.(ABSTRACT TRUNCATED AT 400 WORDS)