Purification and Characterization of Small Molecular Weight Myeloperoxidase from Human Promyelocytic Leukemia HL-60 Cells

Human myeloperoxidase was purified to homogeneity from human promyelocytic leukemia HL-60 cells. A small molecular weight myeloperoxidase was found in these cells and was separated from three other forms of myeloperoxidase of large molecular weight by carboxymethyl-Sepharose CL-6B column chromatography and Sephacryl S-200 gel filtration. The S20,w values of the molecular weights of the small and large myeloperoxidases were found to be 5.2 and 8.07 S, respectively, by sucrose density gradient centrifugation. From these S20,w values, the molecular weights of the small and large myeloperoxidases were estimated to be 79 000 and 153 000, respectively. On electrophoresis in sodium dodecyl sulfate--polyacrylamide gel, the small and large myeloperoxidases each gave two bands of protein corresponding to molecular weights of 59 300 and 10 150. The small myeloperoxidase could not be distinguished from the large enzymes by the Ouchterlony double immunodiffusion test, but it could be distinguished from them by the microcomplement fixation text. One of the three large molecular weight myeloperoxidases was eluted at a lower concentration of methyl alpha-D-mannoside than the other two on concanavalin A--Sepharose chromatography. This suggested that the heterogeneity of the myeloperoxidases with large molecular weight may be partly due to differences in their sugar moieties.