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.
The Cu,Zn superoxide dismutase isoenzymes of Xenopus laevis: purification, identification of a heterodimer and differential heat sensitivity / Capo, Cr; Polticelli, F; Calabrese, Lilia; Schinina', Maria Eugenia; Carri, Mt; Rotilio, G.. - In: BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS. - ISSN 0006-291X. - 173:(1990), pp. 1186-1193. [10.1016/S0006-291X(05)80911-8]
The Cu,Zn superoxide dismutase isoenzymes of Xenopus laevis: purification, identification of a heterodimer and differential heat sensitivity
CALABRESE, Lilia;SCHININA', Maria Eugenia;
1990
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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.