Regulation of Endopolygalacturonate Transeliminase in an Adenosine 3',5'-Cyclic Monophosphate-Deficient Mutant ofErwinia carotovora

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Abstract
A cAMP-deficient mutant of E. carotovora was isolated from a nitrosoguanidine-treated .beta.-galactosidase constitutive strain. The mutant was unable to use .alpha.-lactose, L-arabinose, D-galactose, L-rhamnose, D-xylose, raffinose, D-cellobiose, glycerol and sodium polypectate as sole C sources unless exogenous cAMP was supplied in the medium. The catabolism of D-ribose, D-mannitol and D-glucose was not affected in the cAMP-deficient mutant. The synthesis of the inducible enzyme, endopolygalacturonate transeliminase (PGTE) [EC 4.2.2.2], was under the direct control of the cAMP regulatory mechanism. The cAMP-deficient mutant, growing on a casein hydrolysate-minimal salts medium, produced only low levels of PGTE, even in the presence of the inducer, sodium polypectate. When both sodium polypectate and cAMP were added, the levels of PGTE were elevated to levels comparable with those of the induced parent strain.