title: Alterations in intracellular and extracellular activities of antioxidant enzymes during suspension culture of sweetpotato.
abstract: Cultured plant cells are a good system for the study of antioxidant mechanisms and for the mass production of antioxidants, because they can be grown under conditions of high oxidative stress. Alterations in the intracellular and extracellular activities of three antioxidant enzymes, superoxide dismutase (SOD), guaiacol-type peroxidase (POD), and glutathione peroxidase (GPX), were investigated in suspension cultures of sweetpotato (Ipomoea batatas) during cell growth. Intracellular SOD activities (units/mg protein) at 15 days after subculture (DAS) and 30 DAS were 10 and 20 times higher, respectively, compared with the SOD activity at 1 DAS, whereas intracellular specific POD and GPX activities did not significantly increase until after 15 DAS, when they rapidly increased. The extracellular activities of the three enzymes in culture medium were much higher than were the intracellular activities. The change in extracellular SOD activity was similar to that of extracellular GPX during cell growth. Those activities showed high levels until 5 DAS and then significantly decreased. Extracellular POD activity had an almost constant level regardless of the cell growth stage. In addition, intracellular SOD and POD isozymes were quite different from those isozymes in the culture medium. The changes in SOD and POD isozymes observed here suggest that different isozymes might modulate the levels of reactive oxygen intermediates during cell growth. Characterization of extracellular antioxidant enzymes discovered here would provide a new understanding for defense mechanism in plants.
authors.affiliation: Genome Research Center, Inje University, 607 Obangdong, Gimhae 621-749, Gyungnam, Republic of Korea.
authors.forename: Young-Hwa
authors.initials: YH
authors.lastname: Kim
authors.forename: Yunhee
authors.initials: Y
authors.lastname: Kim
authors.forename: Eunhee
authors.initials: E
authors.lastname: Cho
authors.forename: Sangsoo
authors.initials: S
authors.lastname: Kwak
authors.forename: Sukyoon
authors.initials: S
authors.lastname: Kwon
authors.forename: Jungmyung
authors.initials: J
authors.lastname: Bae
authors.forename: Baekrak
authors.initials: B
authors.lastname: Lee
authors.forename: Byungin
authors.initials: B
authors.lastname: Meen
authors.forename: Gyung-Hye
authors.initials: GH
authors.lastname: Huh
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D018929:Cell Culture Techniques; D049109:Cell Proliferation; D005979:Glutathione Peroxidase / Q000378:metabolism; D027723:Ipomoea batatas / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D009195:Peroxidase / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism; D013997:Time Factors
chemical_list: D000975:Antioxidants; C121048:guaiacol peroxidase; D009195:Peroxidase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase