Giovanna Colombo

Studies on the fructose 1-phosphatase activity of pig kidney fructose 1,6-diphosphatase

Mammalian liver and kidney fructose 1,6-diphosphatase (EC 3.1.3.11) (FDPase) has been shown to catalyze the hydrolysis of the 1-phosphate from fructose 1,6-diphosphate and the next higher homolog, sedoheptulose 1,7-diphosphate [ 1 ]. During the last few years it has also been shown that FDPase catalyzes the hydrolysis of other structurally unrelated substrates, such as/3-glycerophosphate [2], phosphoenol pyruvate [3], and p-nitrophenyl phosphate [4]. However, little attention has been given to earlier indications pointing out that rabbit liver [5] and pig kidney FDPase [6] show some activity with fructose1-P. Since fructose-l-P is formed by fructokinase in those tissues (e.g. liver and kidney) metabolizing fructose [7, 8], it was deemed important to study some parameters of the hydrolysis of fructose-1-P by FDPase, because the concurrent function of both fructokinase (Fructose + ATP ~ Fructose-1-P + ADP) and of FDPase (Fructose-l-P -+ Fructose + Pi) within a single cell compartment could lead to a futile cycle of carbon and a nethydrolysis of ATP.