Interaction between D-glyceraldehyde-3-phosphate dehydrogenase and calmodulin.

The effect of calmodulin on the associative properties of D-glyceraldehyde-3-phosphate dehydrogenase was investigated by means of a covalently attached fluorescent probe. We found that calmodulin shifts the equilibrium between the different forms of glyceraldehyde-3-phosphate dehydrogenase and binds to the subunits with an apparent dissociation constant of 1.8 microM. Within this heterologous complex calmodulin has no effect on the catalytic activity of the enzyme. The formation of the heterocomplex can be modulated by the specific anti-calmodulin drug, trifluoperazine, as well as by aldolase. The possible role of these associations is that they influence the interaction of both glyceraldehyde-3-phosphate dehydrogenase and calmodulin with other soluble proteins or structural elements.