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The proteolytic maturation of prohormone convertase 2 (PC2) is a pH-driven process
N S Lamango1, E Apletalina, J Liu
1Department of Biochemistry and Molecular Biology, Louisiana State University Medical Center, New Orleans, Louisiana, 70112, USA.
Archives of Biochemistry and Biophysics
|February 17, 1999
Summary
Prohormone convertase 2 (proPC2) zymogen activation is an intramolecular, autocatalytic process. This conversion is pH-dependent, occurring in acidic conditions within the secretory pathway, rather than relying on calcium or 7B2 inhibition.
Area of Science:
- Biochemistry
- Cell Biology
- Endocrinology
Background:
- Prohormone convertase 2 (PC2) is crucial for processing neuroendocrine peptides.
- Understanding the activation mechanism of PC2 zymogen (proPC2) is key to its function.
- Recombinant proPC2 can be produced in Chinese hamster ovary (CHO) cells.
Purpose of the Study:
- To characterize the spontaneous conversion of recombinant proPC2 to its active form.
- To elucidate the mechanism and regulatory factors involved in proPC2 zymogen activation.
- To compare the proPC2 conversion process with the activity of mature PC2.
Main Methods:
- Purification of recombinant proPC2 from CHO cell culture medium.
- Enzymatic assays to study proPC2 conversion kinetics.
- Inhibition studies using specific inhibitors (pCMS, 7B2 CT peptide).
- Analysis of calcium dependency and effect of EDTA.
- pH-dependent activity assays.
- Zymogen concentration-dependent rate analysis.
Main Results:
- ProPC2 undergoes a single cleavage at a paired basic site to become active.
- ProPC2 conversion is not inhibited by pCMS or 7B2 CT peptide, unlike mature PC2.
- Activation is independent of calcium and EDTA.
- The conversion rate is concentration-independent, suggesting an intramolecular mechanism.
- Optimal proPC2 conversion occurs between pH 4.0 and 4.9.
Conclusions:
- Cellular proPC2 maturation is an autocatalytic, intramolecular process.
- Activation is primarily regulated by the pH gradient in the secretory pathway.
- This mechanism differs significantly from the regulation of mature PC2 activity.