Synergistic Inhibition of Fructose 1,6‐Bisphosphatase by Fructose 2,6‐Bisphosphate and Adenosine Monophosphate in Round Spermatids of Rats: fructose 1, 6‐bisphosphatase/AMP/fructose 2, 6‐bisphosphate/spermatids/rats

The effects of adenosine monophosphate (AMP) and fructose 2, 6‐bisphosphate (fruc‐2, 6‐P₂) on the key‐enzyme of gluconeogenesis, fructose 1, 6‐bisphosphatase (fruc‐P₂ase; D‐fructose 1, 6‐bisphosphate 1‐phosphohydrolase, EC 3.1.3.11) in spermatid extract from rat testes were studied. The fruc‐P₂ase activity in the spermatids of rats was suppressed by AMP and fruc‐2, 6‐P₂. The inhibition of fruc‐2, 6‐P₂ was much stronger at low than at high substrate concentrations, and enhanced synergistically with AMP. The substrate saturation curve was changed by fruc‐2, 6‐P₂ hyperbolic to sigmoidal. Furthermore, the concentration of AMP that decreased the activity to 50% was much lower in the presence than in the absence of fruc‐2, 6‐P₂. These results indicate the possibility that gluconeogenesis in spermatids of rats is controlled by AMP and fruc‐2, 6‐P₂.