REVERSIBLE ACTIVATION OF HUMAN NEUTROPHIL CALPAIN PROMOTED BY INTERACTION WITH PLASMA-MEMBRANES

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  • 1 January 1985
    • journal article
    • research article
    • Vol. 11  (1) , 35-44
Abstract
Human neutrophil calpain is a monomer of 85 kDa [kilodalton] MW. The proteinase shows an absolute requirement for Ca2+ with maximal catalytic activity at 0.1-0.2 mM Ca2+ and negligible activity at 1-5 .mu.M Ca2+. At this concentration of Ca2+ neutrophil calpain becomes active and reaches 65% of its maximal catalytic activity following interaction with plasma membranes. The activation is fully reversible since the enzyme returns to its native, high Ca2+ requiring form following removal of the membranes. Membrane phospholipids appear to be the physiological compounds responsible for the promotion of such reversible activation. Unlike other Ca2+ dependent proteinases, neutrophil calpain does not undergo conversion to a low Ca2+ requiring form by limited autoproteolysis.