[Molecular constitution of human arylsulfatase A and its alteration in cancer]

Arylsulfatase A (ASA) was purified from human placenta, ovary, and ovarian cancer tissue. The purified ASA was composed of three non-identical peptides of 58 kDa, 50 kDa, and 10 kDa on polyacrylamide gel electrophoresis in the presence of SDS (SDS-PAGE). The N-terminal sequence of the 58 kDa peptide was found to be identical with that of the 50 kDa on analysis with a protein sequencer. The peptide map of the 58 kDa peptide was quite similar to that of the 50 kDa except for some peaks. The 50 kDa peptide lacked the peptide from the residue Val445 to the C-terminus of the amino acid sequence deduced from the ASA cDNA. Four different peptides yielded by the 10 kDa peptide on HPLC had sequences near the C-terminal side. These results suggest that the 50 kDa peptide and the 10 kDa peptide are yielded by the same peptide as the 58 kDa peptide on proteolytic processing. Ovarian ASA showed the same pattern on SDS-PAGE as placental ASA. Ovarian cancer ASA was mainly composed of the 58 kDa band, and in addition the 50 kDa band decreased. The carbohydrate chain of ovarian cancer ASA was more resistant to endo-beta-N-acetylglucosaminidase H than that of normal ovary. These finding suggest that the processing of both the oligosaccharide chains and the protein unit is modified in ovarian cancer.