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)