THE EFFECT OF SEROTONIN (5-HYDROXYTRYPTAMINE) ON GLYCOLYSIS IN THE PERFUSED VENTRICLE OF THE FRESH-WATER BIVALVE ANODONTA-CYGNEA - EVIDENCEFOR PHOSPHORYLATION DEPHOSPHORYLATION CONTROL OF PHOSPHOFRUCTOKINASE
B. Michaelidis et al., THE EFFECT OF SEROTONIN (5-HYDROXYTRYPTAMINE) ON GLYCOLYSIS IN THE PERFUSED VENTRICLE OF THE FRESH-WATER BIVALVE ANODONTA-CYGNEA - EVIDENCEFOR PHOSPHORYLATION DEPHOSPHORYLATION CONTROL OF PHOSPHOFRUCTOKINASE, Journal of Experimental Biology, 180, 1993, pp. 15-25
The ventricles of the freshwater mollusc Anodonta cygnea were isolated
and perfused with serotonin in order to examine its effect on glycoly
sis. Serotonin induces an increase in the concentration of glycolytic
intermediates. Phosphofructokinase (PFK) preparations from ventricles
perfused with serotonin exhibited an increased sensitivity to activati
on by the substrate fructose 6-phosphate (F6P) and to the activators A
MP and fructose 2,6-bisphosphate (F2,6P2) and a reduced sensitivity to
inhibition by ATP. In vitro phosphorylation/dephosphorylation experim
ents revealed that incubation of PFK preparations from ventricles perf
used with normal saline in the presence of ATP, cyclic AMP and MgCl2 a
lters the degree of activation by F6P. In contrast, when enzyme prepar
ations from ventricles treated with serotonin were incubated in the pr
esence of alkaline phosphatase and MgCl2, PFK showed a reduced sensiti
vity to activation by F6P. Serotonin had no significant effect on the
kinetic properties of PK, while it increased the proportion of the act
ive a form of glycogen phosphorylase. These results indicate that sero
tonin induces an increase in the concentration of glycolytic intermedi
ates in the ventricle of A. cygnea and that this is at least partly du
e to the activation of PFK, possibly via phosphorylation by an endogen
ous cyclic-AMP-dependent protein kinase.