Purification of acid sphingomyelinase from human placenta: Characterization and N-terminal sequence

Human placental acid sphingomyelinase (ASM) was purified by sequential chromatography on Con A-Sepharose, octyl-Sepharose and Matrex gel red A, Final purification to apparent homogeneity was achieved by immunoaffinity chromatography employing polyclonal anti-ASM antibodies. The antibodies also allowed specific detection of ASM by Western blotting at various stages of purification, The ASM activity was enriched about 110 000-fold over that of the crude extract, yielding an enzyme preparation with a specific activity of about 1 mmol/h per mg protein in a detergent-containing assay system, Analysis of the final preparation by SDS-PAGE resulted in a single protein band with a molecular mass of similar to 75 kDa, which was reduced to similar to 60 kDa after complete deglycosylation, Microsequencing of the purified ASM revealed the N-terminal amino acid sequence of the mature placental enzyme.