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J Bacteriol. 1969 November; 100(2): 902-913
Copyright © 1969 American Society for Microbiology. All Rights Reserved.

Catabolite Inhibition: a General Phenomenon in the Control of Carbohydrate Utilization¹

¹ Department of Biology, State University of New York at Buffalo, Buffalo, New York 14214
² Department of Experimental Biology, Roswell Park Memorial Institute, Buffalo, New York 14203

ABSTRACT

When Escherichia coli is grown in synthetic medium with radioactive galactose or lactose as the carbon source, the addition of glucose rapidly inhibited utilization of the radioactive substrate, whether the formation of ¹⁴CO₂ or acid-insoluble products was measured. The inhibition was reversed after the removal of glucose. Experiments with mutants blocked in subsequent steps of galactose and lactose metabolism demonstrated that the inhibition occurs prior to the formation of the first metabolic product. The utilization of a variety of sugars, including maltose, lactose, mannose, galactose, L-arabinose, xylose, and glycerol was inhibited by glucose. Of a number of carbohydrates tested as potential inhibitors, only glucose and, to a lesser extent, glucose-6-phosphate (G-6-P) were capable of inhibiting the utilization of all of the substrates. Glucose did not inhibit G-6-P utilization but G-6-P inhibited glucose utilization. With all substrates, except glycerol, there was a delay before the onset of inhibition by G-6-P. We conclude that E. coli has a general regulatory mechanism, termed catabolite inhibition, which controls the activity of early reactions in carbohydrate metabolism, allowing certain substrates to be utilized preferentially.

¹ Taken in part from a dissertation submitted by J. F. McGinnis to the State University of New York at Buffalo in partial fulfillment of the requirements for the Ph.D. degree.