Heart ornithine decarboxylase from control and isoproterenol-treated rats: kinetic properties, multiple forms and subcellular distribution.

Heart ornithine decarboxylase (ODC) from isoproterenol treated rats was compared to heart ODC from control rats. Isoproterenol administration did not significantly change Km for ornithine, but it induced a marked increase of Vmax, X Km for pyridoxal phosphate (PLP) was somewhat reduced. Both Kornm and Vmax were a function of the dithiothreitol (DTT) concentration, in a similar way for control and stimulated enzyme. Two ODC forms were detected by ion exchange chromatography in both control and isoproterenol treated hearts. In control heart, ODC specific activity was high in cytosol and nucleoli. Isoproterenol administration induced a remarkable increase of the cytosolic enzyme only.