The objective of the proposed research is to increase our knowledge of the function and properties of normal arylsulfatase A. Deficiencies of this enzyme occur in the metachromatic leukodystrophies, while in other conditions, such as, osteoarthritis and certain neoplasms the enzyme is present at greatly elevated levels. The putative function of arylsulfatase A is as a cerebroside sulfatase, but the enzyme also catalyzes the hydrolysis of a number of other naturally occurring sulfate esters. They include a sulfoglycerolipid present in sperm and testis, ascorbic acid 2-sulfate, and tyrosine 0-sulfate. We have recently shown that arylsulfatase A from urine occurs in three forms which differ in pI by only 0.1 pH unit. The enzyme from liver, brain, kidney, testis and placenta occurs in six forms, three with pI's like to urine enzyme and three which are more electronegative. The relative abundance of the six forms vary and tissue specific patterns can be deliniated. Neuraminidase treatment of the urine enzyme did not alter the three-banded pattern, but the liver enzyme was coverted from the six-banded pattern to a three-banded pattern like that of the urine enzyme. This microcharge heterogeneity will be studied in detail. Arylsulfatase A will be purified from different tissues and separated into charge isomers. The enzymatic properties of the isomers will be compared with respect to the ratio of activities toward different substrates as well as the kinetic parameters of the reactions, such as Km, Vmax, and pH optimum. The chemical nature of the charge differences will be sought. Elucidation of the basis for isomers of normal arylsulfatase A should lead to a better understanding of the enzyme deficits and excesses and facilitate the development of remedial measures.
NIH ExPorter
NIH ExPorter