Cloning and physical mapping of the sor genes for L-sorbose transport and metabolism from Klebsiella pneumoniae.

The sor genes of Klebsiella pneumoniae KAY2026, which enable the bacterium to metabolize the ketose L-sorbose, have been cloned on an 8.3kb DNA fragment into the multicopy plasmid, pACYC184. The genes were mapped by restriction analysis, by deletion mapping and by insertion mutagenesis with Tn1725. The corresponding gene products were identified by the maxicell technique. The structural genes sorD, sorA and sorE code for a D-glucitol-6-P dehydrogenase (27 kilodalton (kD)), an Enzymell (EllSor) activity specific for L-sorbose and an L-sorbose-1-P reductase (45kD). Besides these genes for known functions, three additional genes were discovered: sorC, coding for a transcriptional 40kD regulatory protein, and sorF and sorB, coding for two proteins of 14kD and 19kD, respectively, involved in transport. The genes form an operon (gene order sorCpCDFBAE) and are inducible by L-sorbose.