title: A low-calcium-requiring calcium-activated neutral proteinase from human placenta.
abstract: A low-calcium-requiring calcium-activated neutral proteinase (mu CANP) has been purified to homogeneity from human placenta. The purification procedure includes chromatography on DEAE-cellulose, Ultrogel AcA-22 and DEAE-Sephadex in succession. The purified mu CANP is a thiol proteinase and requires calcium for activity. Half-maximal activation occurs at 40 microM calcium. It is a heterodimer with subunits of 74 kDa and 32 kDa. (The placental mCANP has subunits of 70 kDa and 32 kDa.) Mn2+ or Sr2+, in combination with Ca2+, activates the enzyme synergistically. The presence of both mCANP and mu CANP in equal proportion in human placenta is reported for the first time. This will facilitate a comparative study of these two forms of human calcium-activated neutral proteinase, especially their physiological structural and functional interrelationship. Maximal activation of the autolysed mCANP occurs at a calcium concentration much higher than that for mu CANP; and this autolysed mCANP does not cross-react with antiserum against mu CANP, suggesting that the two forms of proteinase are independent species.
mesh_terms: D002118:Calcium / Q000494:pharmacology*; D002154:Calpain / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D002413:Cations, Divalent; D002845:Chromatography; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D006801:Humans; D008670:Metals / Q000494:pharmacology; D010920:Placenta / Q000201:enzymology*; D011247:Pregnancy; D013438:Sulfhydryl Compounds / Q000032:analysis
chemical_list: D002413:Cations, Divalent; D008670:Metals; D013438:Sulfhydryl Compounds; D002154:Calpain; D002118:Calcium