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  • 1
    ISSN: 1432-2048
    Keywords: Key words: Peroxisome ; Pisum (senescence) ; Proteolysis ; Ribulose-1 ; 5 ; -bisphosphate carboxylase/oxygenase ; Senescence ; Xanthine oxidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The degradation of peroxisomal and nonperoxisomal proteins by endoproteases of purified peroxisomes from senescent pea (Pisum sativum L.) leaves has been investigated. In our experimental conditions, most peroxisomal proteins were endoproteolytically degraded. This cleavage was prevented, to some extent, by incubation with 2 mM phenylmethylsulfonylfluoride, an inhibitor of serine proteinases. The peroxisomal enzymes glycolate oxidase (EC 1.1.3.1), catalase (EC 1.11.1.6) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49) were susceptible to proteolytic degradation by peroxisomal endoproteases, whereas peroxisomal manganese superoxide dismutase (EC 1.15.1.1) was not. Ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39) from spinach and urease (EC 3.5.1.5) from jack bean were strongly degraded in the presence of peroxisomal matrices. These results indicate that proteases from plant peroxisomes might play an important role in the turnover of peroxisomal proteins during senescence, as well as in the turnover of proteins located in other cell compartments during advanced stages of senescence. On the other hand, our data show that peroxisomal endoproteases could potentially carry out the partial proteolysis which results in the irreversible conversion of xanthine dehydrogenase into the superoxide-generating xanthine oxidase (EC 1.1.3.22). This suggests a possible involvement of the peroxisomal endoproteases in a regulated modification of proteins.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5036
    Keywords: arbuscular mycorrhizal fungi ; isozymes ; nodules ; Pisum sativum ; proteins ; superoxide dismutase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract There are few reports in relation to the role of specific proteins in the mycorrhizal symbiosis. Among the changes in the protein expression as a consequence of the arbuscular mycorrhizal symbiosis, only one case related to changes in superoxide dismutase (SOD; EC 1.15.1.1) activity has been reported in the red clover-Glomus mosseae symbiosis. In this paper, the symbiotic system formed by a leguminous plant,Pisum sativum, and the fungusGlomus mosseae is studied in terms of protein patterns and SOD activity in both mycorrhizal and non-mycorrhizal roots. Our results show that among the differential polypeptides separated by SDS-PAGE, one with a molecular weight of 32.0 kDa, and a protein with an isoelectric point of pI 4.9 appeared strongly expressed in mycorrhizal roots. A partial purification of the related polypeptide could be achieved by DEAE-cellulose chromatography. A higher SOD activity was also detected in mycorrhizal pea roots, although both mycorrhizal and non-mycorrhizal roots showed the same isoenzymatic pattern for SODs: two Mn-SODs (I and II) and two Cu,Zn-SODs (I and II) were detected, Cu,Zn-SOD I being the most abundant isozyme in both types of roots. A similar pattern of SOD isozymes (Mn-SODs I and II, and Cu,Zn-SODs I and II) was also found in nodules of mycorrhizal and non-mycorrhizal pea roots. However, in nodules Mn-SOD II was the main isozyme. The bacterial nature of this isozyme is postulated in this report.
    Type of Medium: Electronic Resource
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