Coordinated Action of Pectinesterase and Polygalacturonate Lyase Complex of Clostridium multifermentans

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Abstract
The polygalacturonate lyase and pectinesterase activities of C. multifermentans, both produced extracellularly when the organism grows on pectin or polygalacturonate, were 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, the steady-state concentration of lyase substrate expected during action of the 2 sites on pectin if the sites are independent was calculated. No such steady-state concentration of lyase substrate was observed. The 2 types of active site apparently 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 2 sites may represent a system of general significance in synthesis and degradation of biological polymers.