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Purification and characterization of small molecular weight myeloperoxidase from human promyelocytic leukemia HL-60
Abstract:
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.
Insights
Researchers identified a small molecular weight human myeloperoxidase (MPO) in HL-60 cells, distinct from larger MPO forms. This discovery advances understanding of MPO heterogeneity in leukemia.
Area of Science:
- Biochemistry
- Cell Biology
- Hematology
Background:
- Human myeloperoxidase (MPO) is a key enzyme in neutrophil function.
- HL-60 cells, derived from human promyelocytic leukemia, are a model for myeloid differentiation.
- Understanding MPO heterogeneity is crucial for comprehending its role in disease.
Purpose of the Study:
- To purify and characterize different molecular weight forms of human myeloperoxidase (MPO) from HL-60 cells.
- To investigate the structural and potential functional differences between small and large MPO variants.
Main Methods:
- Purification of MPO using carboxymethyl-Sepharose CL-6B chromatography and Sephacryl S-200 gel filtration.
- Determination of molecular weights and sedimentation coefficients (S20,w) via sucrose density gradient centrifugation.
- Analysis of subunit composition using SDS-polyacrylamide gel electrophoresis.
- Immunological characterization using Ouchterlony double immunodiffusion and microcomplement fixation tests.
- Assessment of glycosylation differences via concanavalin A-Sepharose chromatography.
Main Results:
- A distinct small molecular weight MPO was isolated and separated from three larger MPO forms.
- Sedimentation coefficients indicated molecular weights of 79,000 for small MPO and 153,000 for large MPO.
- SDS-PAGE revealed subunit compositions of 59,300 and 10,150 for both small and large MPO forms.
- Immunological tests showed similarities (Ouchterlony) but also differences (microcomplement fixation) between MPO forms.
- Concanavalin A chromatography suggested glycosylation heterogeneity among the large MPO variants.
Conclusions:
- Human HL-60 cells contain multiple molecular weight forms of myeloperoxidase, including a previously unidentified small form.
- The heterogeneity of large MPO forms may be partly attributed to variations in their carbohydrate moieties.
- These findings highlight the complexity of MPO structure and suggest potential for differential functions.