title: The Cu,Zn superoxide dismutase isoenzymes of Xenopus laevis: purification, identification of a heterodimer and differential heat sensitivity.
abstract: The three Cu,Zn superoxide dismutase electromorphs of the amphibian Xenopus laevis were purified by an original procedure. N-terminal sequence analysis demonstrated that they are two different homodimers (AA and BB) and a hybrid heterodimer (AB), arising from the co-expression of duplicated genes. The three forms have the same pI, same enzyme activity and EPR spectra, but different heat-sensitivity, form BB being more resistant than form AA, with form AB showing intermediate sensitivity. Thermostability of BB and the control bovine enzyme was enhanced by a tenfold increase in protein concentration. It is suggested that the higher heat sensitivity of the AA isoenzyme is related to the presence of an extra Cys residue and to an easier dissociation of the protein dimer into monomers.
authors: Department of Biochemical Sciences, University of Rome, La Sapienza, Italy.
authors: C R
authors: CR
authors: Capo
authors: F
authors: F
authors: Polticelli
authors: L
authors: L
authors: Calabrese
authors: M E
authors: ME
authors: Schinina
authors: M T
authors: MT
authors: Carri
authors: G
authors: G
authors: Rotilio
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002852:Chromatography, Ion Exchange; D004789:Enzyme Activation; D006358:Hot Temperature; D007525:Isoelectric Focusing; D007527:Isoenzymes / Q000032:analysis; D008969:Molecular Sequence Data; D012680:Sensitivity and Specificity; D013482:Superoxide Dismutase / Q000032:analysis*; D014982:Xenopus laevis
chemical_list: D007527:Isoenzymes; D013482:Superoxide Dismutase