title: 1H-NMR characterization of cucumber peroxidases.
abstract: Two peroxidase isoenzymes from Cucumber seedlings, one acidic (pI = 4) and one basic (pI = 9), were characterized by 1H-NMR spectroscopy. The NMR spectra were obtained in the native (ferric high-spin) and cyanide ligated (ferric low-spin) forms of both isoenzymes. The NMR spectral comparison of paramagnetically shifted resonances with those of the well characterized horseradish peroxidase C, HRP(C), isoenzyme indicates that both cucumber peroxidases have a protohemin IX prosthetic group with proximal histidine coordinated to the heme iron. The downfield heme 1H-NMR shift pattern is distinct for each isoenzyme, and this reflects presumably dissimilar heme active site environments. The basic isoenzyme shows less asymmetry in heme 1H-NMR signals as compared to the acidic isoenzyme or HRP(C) isoenzyme. It was also found that the acidic cucumber peroxidase exists predominantly as a monomeric species in solution with 30 kDa molecular mass as opposed to its earlier characterization as a 60 kDa dimeric protein.
authors.affiliation: Department of Chemistry, University of Iowa, Iowa City 52242.
authors.forename: L B
authors.initials: LB
authors.lastname: Dugad
authors.forename: H M
authors.initials: HM
authors.lastname: Goff
authors.forename: F B
authors.initials: FB
authors.lastname: Abeles
mesh_terms: D001665:Binding Sites; D007526:Isoelectric Point; D007527:Isoenzymes / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D010544:Peroxidases / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry; D010944:Plants / Q000201:enzymology*
chemical_list: D007527:Isoenzymes; D010940:Plant Proteins; D010544:Peroxidases