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The L-arabinose operon, also called the ara or araBAD operon, is an operon required for the breakdown of the five-carbon sugar L-arabinose in Escherichia coli. The L-arabinose operon contains three structural genes: araB, araA, araD , which encode for three metabolic enzymes that are required for the metabolism of L-arabinose. AraB , AraA , AraD produced by these genes catalyse conversion of L-arabinose to an intermediate of the pentose phosphate pathway, D-xylulose-5-phosphate.
The structural genes of the L-arabinose operon are transcribed from a common promoter into a single transcript, a mRNA. The expression of the L-arabinose operon is controlled as a single unit by the product of regulatory gene araC and the catabolite activator protein -cAMP complex. The regulator protein AraC is sensitive to the level of arabinose and plays a dual role as both an activator in the presence of arabinose and a repressor in the absence of arabinose to regulate the expression of araBAD. AraC protein not only controls the expression of araBAD but also auto-regulates its own expression at high AraC levels.