Biosynthesis of secreted beta-hexosaminidase in Tetrahymena thermophila. A comparison of the wild type with a secretory mutant

Biochem J. 1988 Jun 15;252(3):837-42. doi: 10.1042/bj2520837.

Abstract

The synthesis and secretion of beta-hexosaminidase was studied in wild type and secretion-deficient Tetrahymena thermophila cells by metabolic labelling and immunoprecipitation. beta-Hexosaminidase is synthesized as a Mr 79,000 polypeptide which is within 10 min converted into a Mr 59,000 form. The Mr 59,000 polypeptide is further processed (within 20 min) into at least three major mature forms of Mr 58,000-54,000, which are almost quantitatively secreted into the culture medium within 1-2 h after their synthesis. Both precursor and mature forms contain asparagine-linked oligosaccharide chains which are cleavable by endoglucosaminidase F, but not by endoglucosaminidase H. Neither [32P]orthophosphate nor [35S]sulphate are incorporated into immunoprecipitable precursor and mature beta-hexosaminidases, suggesting the absence of a phosphorylated recognition marker. Biosynthesis and processing of beta-hexosaminidase is apparently unaltered in the secretory mutant MS-1; however the processed polypeptides remain cellular bound in the mutant, indicating that the mutation affects a late event in the secretion pathway of lysosomal enzymes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cells, Cultured
  • Chemical Precipitation
  • Electrophoresis, Polyacrylamide Gel
  • Mutation
  • Oligosaccharides / analysis
  • Peptide Fragments / analysis
  • Peptides / metabolism
  • Tetrahymena / enzymology*
  • Tetrahymena / genetics
  • beta-N-Acetylhexosaminidases / biosynthesis*
  • beta-N-Acetylhexosaminidases / immunology

Substances

  • Oligosaccharides
  • Peptide Fragments
  • Peptides
  • beta-N-Acetylhexosaminidases