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Physiology and Biochemistry

Regulation of Endopolygalacturonate Transeliminase in an Adenosine 3’,5’-Cyclic Monophosphate-Deficient Mutant of Erwinia carotovora. M. S. Mount, Associate professor, Department of Plant Pathology, University of Massachusetts, Amherst, MA 01003; P. M. Berman(2), R. P. Mortlock(3), and J. P. Hubbard(4). (2)(4)Research assistant, and professor, respectively, Department of Plant Pathology, University of Massachusetts, Amherst, MA 01003; (3)Graduate research assistant, Department of Microbiology, University of Massachusetts, Amherst, MA 01003. Phytopathology 69:117-120. Accepted for publication 9 August 1978. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-117.

An adenosine 3’,5’-cyclic monophosphate (cAMP)-deficient mutant of Erwinia carotovora was isolated from a nitrosoguanidine-treated β-galactosidase constitutive strain. The mutant was unable to use α-lactose, L-arabinose, D-galactose, L-rhamnose, D-xylose, raffinose, D-cellobiose, glycerol, and sodium polypectate as sole carbon 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), 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, however, the levels of PGTE were elevated to levels comparable with those of the induced parent strain.