title: Coordinated action of pectinesterase and polygalacturonate lyase complex of Clostridium multifermentans.
abstract: The polygalacturonate lyase and pectinesterase activities of Clostridium multifermentans, both produced extracellularly when the organism grows on pectin or polygalacturonate, have been suggested to be associated in a single complex. Both enzymic sites act on their respective substrates by single-chain action patterns, as shown by equivalent release of terminal tritium label and total product throughout the reaction. From these results, the Km and V of the lyase, and the amount of lyase activity present, we calculate the steady-state concentration of lyase substrate expected during action of the two sites on pectin if the sites are independent. No such steady-state concentration of lyase substrate was observed. Therefore, we conclude that the two types of active site act in a coordinated manner; the polysaccharide chain passes from the esterase site to the lyase site without intermediate dissociation and rebinding. This 'molecular disassembly line' constituted by the two sites may represent a system of general significance in synthesis and degradation of biological polymers.
mesh_terms: D001665:Binding Sites; D002265:Carboxylic Ester Hydrolases / Q000302:isolation & purification / Q000378:metabolism*; D003013:Clostridium / Q000201:enzymology*; D007700:Kinetics; D046911:Macromolecular Substances; D009097:Multienzyme Complexes / Q000378:metabolism*; D011133:Polysaccharide-Lyases / Q000302:isolation & purification / Q000378:metabolism*; D011485:Protein Binding
chemical_list: D046911:Macromolecular Substances; D009097:Multienzyme Complexes; D002265:Carboxylic Ester Hydrolases; D011133:Polysaccharide-Lyases