Chalcone synthases from spinach (Spinacia oleracea L.) : I. Purification, peptide patterns, and immunological...

The two chalcone-synthase forms from leaves ofSpinacia oleracea L. were purified to apparent homogeneity. Antibodies were raised against both proteins in rabbits. The specificity of the antibodies was tested using immunotitration, immunoblotting, and immunoelectrophoresis techniques. The antibodies exhibited exclusive specificity for chalcone synthase and did not discriminate between the two antigens. The homodimeric chalcone synthases had the same subunit molecular weight but differed in their apparent native molecular weights. The peptide maps indicated extensive homology between the proteins. Chalcone-synthase activity was not detected in isolated spinach chloroplasts. Both enzyme forms were present in spinach cell-suspension cultures in which they were induced by light.