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A1M/α1-microglobulin is proteolytically activated by myeloperoxidase, binds its heme group and inhibits low density

Martin Cederlund1, Adnan Deronic2, Jan Pallon3

  • 1Division of Infection Medicine, Department of Clinical Sciences, Lund University Lund, Sweden.

Frontiers in Physiology
|February 21, 2015
PubMed

Insights

Alpha1-microglobulin (A1M) is cleaved by myeloperoxidase (MPO) into a truncated form (t-A1M). This interaction inhibits MPO-driven low-density lipoprotein (LDL) oxidation, protecting tissues from inflammatory damage.

Area of Science:

  • Biochemistry
  • Immunology
  • Oxidative Stress Research

Background:

  • Alpha1-microglobulin (A1M) is an antioxidant protein with reductase and radical-binding functions.
  • Neutrophil myeloperoxidase (MPO) releases reactive oxygen species during inflammation, contributing to atherosclerosis via LDL oxidation.

Purpose of the Study:

  • To investigate the interaction between A1M and MPO.
  • To determine if A1M regulates MPO activity and its oxidative effects.

Main Methods:

  • Incubation of A1M with MPO under varying pH, time, and substrate concentrations.
  • Analysis of A1M cleavage products, including iron and heme-degradation products.
  • Assessment of A1M's inhibitory effect on MPO- and hydrogen peroxide-induced LDL oxidation.

Main Results:

  • A1M undergoes proteolytic cleavage by MPO, forming truncated A1M (t-A1M).
  • The cleavage reaction is dependent on pH, time, and substrate concentration, with optimal cleavage at pH 7.
  • t-A1M contains iron and heme-degradation products.
  • A1M effectively inhibits MPO- and H2O2-induced LDL oxidation.

Conclusions:

  • A1M interacts with MPO, leading to its proteolytic modification.
  • A1M acts as an inhibitor of MPO activity, specifically preventing LDL oxidation.
  • A1M may play a protective role against inflammatory damage caused by the neutrophil respiratory burst.
Keywords:
C-terminal proteolysisheme bindinglow density lipoproteinmyeloperoxidaseneutrophilsα1-microglobulin

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