An alpha-mercaptoacrylic acid derivative is a selective nonpeptide cell-permeable calpain inhibitor and is neuroprotective.

Overactivation of calcium-activated neutral protease (calpain) has been implicated in the pathophysiology of several degenerative conditions, including stroke, myocardial ischemia, neuromuscular degeneration, and cataract formation. Alpha-mercaptoacrylate derivatives (exemplified by PD150606), with potent and selective inhibitory actions against calpain, have been identified. PD150606 exhibits the following characteristics: (i) Ki values for mu- and m-calpains of 0.

Binding and aggregation of human mu-calpain by terbium ion.

Human mu-calpain is activated maximally by 100-200 microM Ca2+. Both the 80 kDa and 29 kDa subunits of mu-calpain have a EF-hand type calcium-binding domain. It is known that trivalent terbium ion (Tb3+) mimics Ca2+ in many biological systems.

A Coomassie brilliant blue G-250-based colorimetric assay for measuring activity of calpain and other proteases.

The activity of cytosolic calcium-dependent neutral protease (calpain) is commonly measured using casein as a substrate. A novel, modified caseinolysis assay is now developed. It involves incubation of calpain with substrate casein, followed by removal of an aliquot to which Coomassie brilliant blue G-250 dye reagent is added.