ANALYSIS OF THE CBBF GENES FROM ALCALIGENES-EUTROPHUS THAT ENCODE FRUCTOSE-1,6- SEDOHEPTULOSE-1,7-BISPHOSPHATASE/

The cbbF genes of the facultative chemoautotroph Alcaligenes eutrophus H16 are part of two highly homologous cbb operons. Both the chromosom al and the megaplasmid pHG1-borne copy of cbbF were cloned and sequenc ed. Subsequent analyses including comparison with known sequences from other organisms and heterologous expression in Escherichia coli revea led that each of the genes encodes fructose-1,6-bisphosphatase (FBPase ). A closely related activity likewise operating in the Calvin carbon reduction cycle, sedoheptulose-1,7-bisphosphatase, was also catalyzed by the two isoenzymes which were purified from autotrophically grown c ells of A. eutrophus. Two-dimensional gel electrophoresis allowed the separation of the cbbF gene products. preliminary physical evidence by Southern hybridization with a heterologous gene probe was obtained fo r the existence of a third FBPase gene, fbp, on the chromosome of the organism. Its product is probably involved in the heterotrophic carbon metabolism.