Practice question

Arabinose structural genes are organized as contiguous araBAD cluster transcribed as single polycistronic messenger from PBAD promoter under dual control. araB encodes ribulokinase enzyme phosphorylating L-ribulose using ATP producing ribulose-5-phosphate; araA encodes L-arabinose isomerase converting L-arabinose aldose to L-ribulose ketose; araD encodes L-ribulose-5-phosphate 4-epimerase generating D-xylulose-5-phosphate which enters pentose phosphate pathway for energy and biosynthesis. Together three enzymes divert abundant plant-derived pentose sugar into central carbon metabolism. araC regulatory gene transcribed divergently from same intergenic control region forms separate transcription unit with autoregulated PC promoter.