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Biosynthesis and processing of placental alkaline phosphatase
Biochemical and Biophysical Research Communications
|March 16, 1983
Summary
Choriocarcinoma cells synthesize placental alkaline phosphatase (PLAP) precursors and processed forms. PLAP processing involves mannose and glucosamine incorporation, with glucosamine addition occurring during membrane-associated synthesis.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Placental alkaline phosphatase (PLAP) is a key enzyme synthesized by choriocarcinoma cells.
- Understanding PLAP synthesis and processing is crucial for cellular and molecular biology research.
Purpose of the Study:
- To investigate the synthesis and post-translational modification of placental alkaline phosphatase monomer.
- To elucidate the role of microsomal membranes in PLAP processing.
Main Methods:
- Cell-free synthesis using choriocarcinoma mRNA.
- Incorporation studies using radiolabeled mannose and glucosamine.
- Analysis of polypeptide molecular weights using SDS-PAGE.
Main Results:
- Choriocarcinoma cells produce precursor (61.5 kDa) and processed (64.5 kDa) PLAP monomers in vivo.
- Cell-free synthesis yielded a 60 kDa preprotein, which was processed to 61.5 kDa in the presence of microsomal membranes.
- The unglycosylated PLAP monomer has an apparent molecular weight of 58 kDa.
- [3H]Mannose incorporated into both precursor and processed forms, while [3H]glucosamine primarily incorporated into the processed form.
Conclusions:
- PLAP synthesis involves a preprotein form that is processed to a precursor form (61.5 kDa) via membrane-associated glycosylation.
- Further processing to the mature 64.5 kDa form involves the addition of glucosamine moieties.