The effect of arabinose 1,5-bisphosphate on rat hepatic 6-phosphofructo-1-kinase and fructose-1,6-bisphosphatase

The α- and β-anomers of arabinose 1,5-bisphosphate and ribose 1,5-bisphosphate were tested as effectors of rat liver 6-phosphofructo-1-kinase and fructose-1,6-bisphosphatase. Both anomers of arabinose 1,5-bisphosphate activated the kinase and inhibited the bisphosphatase. The α-anomer was the more effective kinase activator while the β-anomer was the more potent inhibitor of the bisphosphatase. Inhibition of the bisphosphatase by both anomers was competitive, and both potentiated allosteric inhibition by AMP. β-Arabinose 1,5-bisphosphate was also more effective in decreasing fructose 2,6-bisphosphate binding to the enzyme. Neither anomer of ribose 1,5-bisphosphate affected 6-phosphofructo-1-kinase or fructose-1,6-bisphosphatase, indicating that the configuration of the C-2 (C-3 in Fru 2,6-P₂) hydroxyl group is important for biological activity. These results are also consistent with arabinose 1,5-bisphosphate binding to the active site and thereby enhancing the interaction of AMP with the allosteric site.