Streller S, Kromer S, Wingsle G
Isolation and Purification of Mitochondrial Mn-Superoxide Dismutase from the Gymnosperm Pinus-Sylvestris L
Plant and Cell Physiology: 1994 35:859-867
Manganese superoxide dismutase (Mn-SOD, EC 126.96.36.199) was purified from germinating seeds of Scots pine (Pinus sylvestris L.) 3 days after the start of imbibition. The purification schedule included (NH4)(2)SO4 fractionation, anion-exchange and hydrophobic-interaction chromatographies and chromatofocusing. Purified Mn-SOD had an apparent specific activity of 4,130 McCord-Fridovich units (mg protein)(-1). The molecular mass of the holoenzyme was estimated to be 91 kDa by size-exclusion chromatography, and a molecular mass of 23 kDa was determined by SDS-PAGE. However, isoelectric focusing demonstrated that the purified enzyme consisted of three similarly migrating isoforms, with isoelectric points of approximately 6.5. NH2-terminal amino acid sequencing of purified Mn-SOD revealed no differences among the three isoforms. The comparison of the first 32 NH2-terminal amino acids with sequences of NH2-terminal amino acids of Mn-SODs from angiosperms reflected the phylogenetic distances between Scots pine, which is a gymnosperm, and angiospermic species. Cell fractionation suggested the mitochondrial localization of Mn-SODs and no evidence for glyoxysomal localization was found. Mn-SOD activity was absent from dry seeds. It was detectable at a considerable level after imbibition for 24 h, and it was again absent from 3-week-old seedlings.
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