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J Bacteriol. 1974 April; 118(1): 112-120
Copyright © 1974 American Society for Microbiology. All Rights Reserved.

Regulation of Leucine Catabolism in Pseudomonas putida

Linda K. Massey1, Robert S. Conrad2 and John R. Sokatch

a Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73190

ABSTRACT

The generation time of Pseudomonas putida with L-leucine was 20 h in synthetic media but only 3 h with D-leucine. Slow growth in the presence of L-leucine was partially overcome by addition of 0.1 mM amounts of either D-valine, L-valine, or 2-ketoisovalerate. The activities of five enzymes which take part in the oxidation of leucine by P. putida were measured under various conditions of growth. Four enzymes were induced by growth with DL-leucine as sole source of carbon: D-amino acid dehydrogenase, branched-chain keto acid dehydrogenase, 3-methylcrotonyl-coenzyme A carboxylase, and 3-hydroxy-3-methylglutaryl-coenzyme A lyase. The segment of the pathway required for oxidation of 3-methylcrotonate was induced by growth on isovalerate or 3-methylcrotonate without formation of the preceding enzymes. The synthesis of carboxylase and lyase appeared to have been repressed by the addition of L-glutamate or glucose to cells growing on DL-leucine as the sole carbon source. Mutants unable to grow at the expense of isovalerate had reduced levels of carboxylase and lyase, whereas the levels of three enzymes common to the catabolism of all three branched-chain amino acids and those of two isoleucine catabolic enzymes were normal.


FOOTNOTES

1 Present address: Oklahoma Medical Research Foundation, Oklahoma City, Okla. 73104.

2 Present address: Department of Microbiology, Baylor University College of Medicine, Houston, Tex. 77025.


J Bacteriol. 1974 April; 118(1): 112-120
Copyright © 1974 American Society for Microbiology. All Rights Reserved.




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