Key enzymes of gluconeogenesis, D-glucose-6-phosphatase (G-6-Pase) [EC 3.1.3.9] and D-fructose-1,6-bisphosphate 1-phosphohydrolase (Fru-1,6-Pase) [EC 3.1.3.11], were investigated in Helix pomatia L. and Pomacea bridgesii (Reeve). Fru-1,6-Pase and G-6-Pase activities were determined measuring with malachite green the concentration of inorganic phosphate produced by substrate hydrolysis in homogenates of hepatopancreas, kidney and foot muscle. Determined Fru-1,6-Pase activities (U/g wt.) in H. pomatia were as follows: hepatopancreas 1.01, kidney 0.19, foot muscle 0.24, in P. bridgesii the respective values were: 0.94, 0.34 and 0.22. Activities of G-6-Pase (U/g wt.) in H. pomatia were: 1.65 in hepatopancreas, 0.64 in kidney and 0.21 in foot muscle, in P. bridgesii the respective values were: 0.79, 0.31, 0.21. Thus the highest gluconeogenic capacity in both species was found in hepatopancreas. Fru-1,6-Pase from H. pomatia and P. bridgesii hepatopancreas was inhibited by AMP. Determined I0.5 were 8.4
M for H. pomatia and 7.3
M for P. bridgesii, and the values were comparable with those of mammalian liver Fru-1,6-Pase. Km determined for hepatopancreas G-6-Pase from H. pomatia and P. bridgesii were 1.3 mM and 4.1 mM, respectively and were also comparable with Km of mammalian liver enzyme.