title: Functional alpha 2-macroglobulin half-molecules induced by cadmium.
abstract: Human alpha 2-macroglobulin can be reversibly dissociated by Cd2+ at low ionic strength in half-molecules which retain their ability to bind tightly plasmin and chymotrypsin. The steady state kinetic parameters of these proteinases towards chromogenic substrates when bound to half-molecules are not greatly different from those determined for these enzymes linked to whole alpha 2M molecules. Cd2+ can also induce the dissociation of plasmin- and chymotrypsin - alpha 2M complexes into proteinase-alpha 2M half-molecule conjugates. These results, taken with the fact that monomeric units of alpha 2M cannot bind these proteinases, strongly suggest that each active site of alpha 2M consists in a specific arrangement of two monomeric units linked by disulfide bridges.
mesh_terms: D001665:Binding Sites; D002104:Cadmium / Q000494:pharmacology*; D002918:Chymotrypsin / Q000378:metabolism; D005341:Fibrinolysin / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D000511:alpha-Macroglobulins / Q000032:analysis* / Q000378:metabolism
chemical_list: D000511:alpha-Macroglobulins; D002104:Cadmium; D002918:Chymotrypsin; D005341:Fibrinolysin