Distinct chromatographic forms of human hemi-myeloperoxidase obtained by reductive cleavage of the dimeric enzyme. Evidence for subunit heterogeneity.

摘要: The enzyme myeloperoxidase (MPO) is a functionally important glycoprotein of neutrophilic granulocytes and occurs in three major isoforms (forms 1, 2, 3) that are dimeric structures composed two heavy subunit-light subunit protomers, each which associated with chlorine-like prosthetic group. In the present study, highly purified MPO were obtained from cells single normal donor, protein was subjected to reductive alkylation under nondenaturing conditions. resulting enzymatically active protomers separated unreacted dimer using gel filtration chromatography. Use fast liquid chromatography cation exchange system Mono S matrix revealed heterogeneity allowed essentially complete resolution form 2. Sodium dodecyl sulfate-polyacrylamide electrophoresis resolved protomeric species reducing conditions small but reproducible differences Mr their subunits (59,000 57,000). Treatment either endo-beta-N-acetylglucosaminidase or peptide N-glycohydrolase F reduced by approximately 3000 did not change relative electrophoretic mobilities. Heavy light prepared full retention group subunit. Reverse-phase amino-terminal sequencing showed isoform contained one several minor species. No peroxidatic activity inhibition salicylhydroxamic acid observed among any latter considerably more heat labile than forms monomeric isolated HL-60 cells. This first report isolation partial characterization distinct human suggests structure complex considered previously.