cDNA Sequence and Kinetic Properties of Human Lung Fructose(1,6)bisphosphatase

A cDNA encoding fructose(1,6)bisphosphatase was isolated from total human lung RNA. The cDNA contained an open reading frame encoding 337 amino acids. The determined nucleotide sequence of the lung cDNA was significantly different from muscle cDNA and slightly differed from human liver cDNA in a single mutation (Gly-336 for Ala-336) and a T for C substitution in position 648. The human lung fructose(1,6)bisphosphatase [Fru(1,6)Pase] was isolated and its kinetic parameters were compared with liver and muscle isoenzymes. Values ofkcatfor the lung Fru(1,6)Pase were lower than for the liver and muscle enzyme. Like the liver isoenzyme, lung Fru(1,6)Pase is significantly less inhibited by AMP than the muscle enzyme. The values ofI0.5were 9.5, 9.8, and 0.3 μM for the liver, lung, and muscle enzyme, respectively. The lung enzyme was slightly more sensitive to fructose(2,6)bisphosphate [Fru(2,6)P2] inhibition than the liver enzyme.Kiwas 75 μM for the lung and 96 μM for the liver enzyme. The synergistic effect of AMP and Fru(2,6)P2on the lung and liver Fru(1,6)Pase was also observed. In the presence of AMP the corresponding values ofKifor Fru(2,6)P2were 16 μM for the lung and 10 μM for the liver enzyme.