title: The reversible activation by Mn2+ ions of the Ca2+-requiring neutral proteinase of human erythrocytes.
abstract: Mn2+ (50 microM) satisfies the requirement for activity of the purified Ca2+-dependent neutral proteinase from human erythrocytes. Unlike the activation by Ca2+ [E. Melloni et al. (1984) Biochem. Int. 8, 477-489], the effect of Mn2+ is fully reversible and does not involve autodigestion of the native 80-kDa catalytic subunit. However, the native dimeric proenzyme (procalpain), which contains both the 80-kDa subunit and a smaller 30-kDa subunit, is not activated by Mn2+ alone but also requires the presence of micromolar concentrations of Ca2+. Under these conditions, 40% of the maximum activity is expressed without dissociation of the 80- and 30-kDa subunits. Mn2+, but not micromolar Ca2+, can also partially satisfy the metal requirement of the native 80-kDa subunit isolated after dissociation of the heterodimer. This activity is further enhanced by the addition of 5 microM Ca2+, which is ineffective in the absence of Mn2+. After procalpain is converted to active calpain by incubation with Ca2+ and substrate [S. Pontremoli et al. (1984) Biochem. Biophys. Res. Commun. 123, 331-337] full activity is observed with 5 microM Mn2+, which now substitutes completely for Ca2+. Activation of procalpain by Mn2+ represents a new mechanism for modulation of the Ca2+-dependent proteinase activity.
authors.forename: S
authors.initials: S
authors.lastname: Pontremoli
authors.forename: B
authors.initials: B
authors.lastname: Sparatore
authors.forename: F
authors.initials: F
authors.lastname: Salamino
authors.forename: M
authors.initials: M
authors.lastname: Michetti
authors.forename: E
authors.initials: E
authors.lastname: Melloni
mesh_terms: D002118:Calcium / Q000494:pharmacology; D002154:Calpain; D004357:Drug Synergism; D004533:Egtazic Acid / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D010450:Endopeptidases / Q000097:blood*; D004789:Enzyme Activation; D004792:Enzyme Precursors / Q000378:metabolism*; D004912:Erythrocytes / Q000201:enzymology*; D006801:Humans; D046911:Macromolecular Substances; D008345:Manganese / Q000494:pharmacology*; D008970:Molecular Weight
chemical_list: D004792:Enzyme Precursors; D046911:Macromolecular Substances; D008345:Manganese; D004533:Egtazic Acid; D010450:Endopeptidases; D002154:Calpain; D002118:Calcium