[77] The isolation and properties of CAP, the catabolite gene activator

Publisher Summary This chapter discusses the isolation and properties of catabolite activator protein (CAP), the catabolite gene activator. Catabolite repression involves the inhibition of enzyme induction by glucose or its derivatives such as glucose 6-phosphate, fructose, or glycerol. The extent of inhibition is dependent on the bacterial strain, the repressing catabolite, and the growth conditions. The bacterial enzyme galactozymase disappears from cells grown in the presence of glucose. When bacteria is placed in the presence of two sugars, glucose and lactose, maltose, or xylose, a diphasic growth curve ensues. Cyclic adenosine 3',5'-monophosphate (cAMP) linked to the glucose effect. It is useful to assay the CAP at various stages during purification. The transcription assay in which the DNA-directed synthesis of β -gal is measured is the most sensitive and selective assay to use.