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Related Experiment Videos

Opacity factor from group A streptococci is an apoproteinase.

G A Saravani1, D R Martin

  • 1National Health Institute, Poriua, New Zealand.

FEMS Microbiology Letters
|March 1, 1990
PubMed
Summary

Opacity factor (OF), an enzyme from group A streptococci, breaks down high-density lipoprotein (HDL). This enzyme specifically cleaves apoprotein AI in HDL, causing serum opalescence and altering HDL structure.

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Area of Science:

  • Biochemistry
  • Enzymology
  • Microbiology

Background:

  • Certain group A streptococci produce an opacity factor (OF).
  • OF causes opalescence in mammalian sera and was previously thought to be a lipoproteinase.
  • Lipoprotein catalysis involves numerous enzymes, necessitating precise OF identification.

Purpose of the Study:

  • To identify the specific enzymatic activity of opacity factor (OF).
  • To elucidate the mechanism by which OF causes serum opalescence.
  • To characterize the interaction of OF with high-density lipoprotein (HDL).

Main Methods:

  • Enzymatic assays to determine OF activity on serum components.
  • Electrophoretic analysis to assess changes in HDL mobility.
  • Electron microscopy to visualize structural alterations in HDL.
  • SDS-PAGE to analyze protein fragments after OF treatment.

Main Results:

  • OF rendered high-density lipoprotein (HDL) insoluble, causing serum opalescence.
  • OF altered the electrophoretic mobility and molecular shape of HDL.
  • OF specifically cleaved apoprotein AI of HDL into two fragments.

Conclusions:

  • Opacity factor (OF) functions as an apoproteinase, not solely a general lipoproteinase.
  • OF's specific action on apoprotein AI is responsible for the observed opalescence in serum.
  • OF represents a novel class of streptococcal enzymes targeting HDL structure.

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