Structural-functional relationships in pig heart AMP-deaminase in the presence of ATP, orthophosphate, and phosphatidate bilayers.

The secondary structure of pig heart AMP-deaminase (AMP-d) in the absence and in the presence of orthophosphate or dioleoyl phosphatidic acid (DOPA) or ATP was investigated by FT-IR spectroscopy. While the latter substance activates the enzyme, orthophosphate is a well-known negative allosteric effector and DOPA exerts a noncompetitive inhibition on AMP-deaminase. Small changes in the secondary structure of AMP-d were induced by the above mentioned substances. Only DOPA reduced the thermal stability of AMP-d and avoided protein intermolecular interactions suggesting structural-functional relationships in AMP-d in the presence of the above substances and a possible role of phosphatidic acid in the subtle regulation of AMP-d activity by temporary binding of the enzyme to cellular membranes.