The calpain cascade: μ-calpain activates m-calpain

Peter Tompa, Andrea Baki, Éva Schád, Peter Friedrich

Research output: Article

47 Citations (Scopus)


m-Calpain, which usually requires near-millimolar Ca2+ for activation, undergoes autolysis at 25 μM Ca2+ in the presence of μ-calpain. m- Calpain in itself exhibits no sign of autolysis around this Ca2+ concentration. Half-maximal rate of the reaction occurs at 30 μM Ca2+, showing that it is μ-calpain that catalyzes the limited proteolysis of m- calpain in an intermolecular reaction ('heterolysis'). This heterolytic step is accompanied by the activation of m-calpain: μ- and m-calpain preincubated together at 25 μM Ca2+ show significantly higher activity than the sum of activities of μ- and m-calpains preincubated separately. m-Calpain is sensitized to Ca2+ by μ-calpain-mediated activation: the half-maximal value of 160 μM for activation is lowered to 64 μM, which is similar to the shift found in m-calpain autoactivation. We suggest that these in vitro observations are relevant in vivo and the calpain cascade may play an important role in coordinating the functioning of calpains in living cells.

Original languageEnglish
Pages (from-to)33161-33164
Number of pages4
JournalJournal of Biological Chemistry
Issue number52
Publication statusPublished - dec. 1 1996

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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