catabolite repression


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ca·tab·o·lite re·pres·sion

the decreased expression of an operon because of elevated levels of a catabolite of a biochemical pathway.

catabolite repression

REPRESSION of certain INDUCIBLE ENZYME systems by the presence of specific carbon sources, such as GLUCOSE, that the organism prefers to metabolize. For example, in bacteria, EXPRESSION of the LAC OPERON, concerned with the enzymes for the breakdown of LACTOSE, is repressed in the presence of glucose, even though inducers of the operon are available. When the glucose is used up, expression of the lactose operon can be induced. Catabolite repression is important to the efficient running of the cell, because glucose can be metabolized directly in GLYCOLYSIS without the need to expend energy inducing the synthesis of those enzymes required to metabolize the lactose. See also OPERON MODEL.
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Catabolite repression of chitinase and other genes involved in utilization of carbon sources was identified in ccrA1 mutant of S.
Disruption of reg1 gene relieved the carbon catabolite repression of both [+ or -]-amy lases and chitinases indicating the involvement of reg1 (109).
Tomita, Induction and Catabolite Repression Mechanisms of Cellulase in Fungi, J.
Ramon, Carbon Catabolite Repression of the Aspergillus nidulans xlnA gene, Mol.
These results might be attributed to the fact that the presence of readily available substrates has been noted to influence the biosynthesis of many extracellular enzymes via catabolite repression mechanism (Vijayaraghavan et al., 2011; Teodoro and Martins, 2000).
Afterwards, enzyme activity declined due to decrease in nutrients availability in the medium, or carbon catabolite repression, as the expression in yeast is checked by the presence of monosaccharides like glucose and fructose as reported by Samia (2008).
As monosaccharide concentration in the medium decreased to a value below 0.2 mg/ml, carbon catabolite repression was halted resulting in a faster rate of enzyme biosynthesis as reported by Roitsch et al.
These results appear to support catabolite repression by glucose and sorbitol with prodigiosin production.
The decreased activity in the later phase of growth was probably due to catabolite repression by glucose released from starch hydrolysis.
Enzyme production regulation is influenced by catabolite repression. Reduction in enzyme production was observed in the presence of EDTA while addition of tween 20 and CaCl2 helped to enhance the enzyme production.
Decrease in biomass with high xylose concentration may be due to catabolite repression during aerobic metabolism.