Cloning and expression of chromosomally and plasmid-encoded glyceraldehyde-3-phosphate dehydrogenase genes from the chemoautotrophAlcaligenes eutrophys

Hybridizations using heterologous glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene probes suggested the existence of three GAPDH genes in Alcaligenes eutrophus H16. Two of these, located on the chromosome and the megaplasmid pHG1 of the organism, respectively, mapped about 2.5 kilobase pairs (kb) downstream of the two duplicated CO2 fixation gene clusters (cfx genes). They were identified as GAPDH genes (cfxGc and cfxGp) by cloning and expression in Escherichia coli. These genes encode GAPDH isoenzymes functioning in the Calvin cycle. The third gene (gap) is chromosomally encoded but not linked to the cfxc cluster. Its product is probably involved in heterotrophic carbon metabolism.