Plant peroxidase extracted from Coccinia grandis Lin. （Ivy gourd） was purified from crude extract by ammonium sulfate precipitation, ion-exchange chromatography, and size exclusion chromatography. The purified enzym...Plant peroxidase extracted from Coccinia grandis Lin. （Ivy gourd） was purified from crude extract by ammonium sulfate precipitation, ion-exchange chromatography, and size exclusion chromatography. The purified enzyme preparation exhibited a specific activity of 6106.63 p.mol.minl.mg protein1, while purification fold and yield were 17.45 and 34.70%, respectively. The purified peroxidase was homogenous as judged by native and sodium dodecyl sulfate （SDS） polyacrylamide gel electrophoresis. The molecular weight as determined by gel filtration and SDS-polyacrylamide gel electrophoresis was 45 kD, which suggested that the purified peroxidase contained only one subunit. The apparent Km and Vmax values of the enzyme against phenol were 93 p.M and 561 μmol.min^-1.mg protein^-1, respectively. The temperature and pH optimum for purified peroxidase were 45℃ and pH 6.0, respective. However, it was stable at 30-60℃ and pH 4.0-8.0. The presence of metal ions such as Cu2＋ and Ca2＋ enhanced peroxidase activity. On the other hand, Cr3＋ and Hg2＋ strongly inhibited the enzyme activity at 500 p.M. Sodium dodecyl sulfate reduced a half of peroxidase activity at approximately 3 mM. Ivy gourd was stability in the presence of each urea concentrations. The affinity of the enzyme with different substrates showed as the highest relative activities on gallic acid followed by catechin, ascorbic acid and caffeic acid, respectively.展开更多
Class Ⅲ secretable plant peroxidases occur as a large family of genes in plants with many functions and probable redundancy. In this review we are concentrating on the evidence we have on the catalysis of lignin poly...Class Ⅲ secretable plant peroxidases occur as a large family of genes in plants with many functions and probable redundancy. In this review we are concentrating on the evidence we have on the catalysis of lignin polymerization by class Ⅲ plant peroxidases present in the apoplastic space in the xylem of trees. Some evidence exists on the specificity of peroxidase isozymes in lignin polymerization through substrate specificity studies, from antisense mutants in tobacco and poplar and from tissue and cell culture lines of Norway spruce （Picea abies） and Zinnia elegans. In addition, real time （RT-）PCR results have pointed out that many peroxidases have tissue specific expression patterns in Norway spruce. Through combining information on catalytic properties of the enzymes, on the expression patterns of the corresponding genes, and on the presence of monolignols and hydrogen peroxide in the apoplastic space, we can show that specific peroxidases catalyze lignin polymerization in the apoplastic space of Norway spruce xylem.展开更多
文摘Plant peroxidase extracted from Coccinia grandis Lin. （Ivy gourd） was purified from crude extract by ammonium sulfate precipitation, ion-exchange chromatography, and size exclusion chromatography. The purified enzyme preparation exhibited a specific activity of 6106.63 p.mol.minl.mg protein1, while purification fold and yield were 17.45 and 34.70%, respectively. The purified peroxidase was homogenous as judged by native and sodium dodecyl sulfate （SDS） polyacrylamide gel electrophoresis. The molecular weight as determined by gel filtration and SDS-polyacrylamide gel electrophoresis was 45 kD, which suggested that the purified peroxidase contained only one subunit. The apparent Km and Vmax values of the enzyme against phenol were 93 p.M and 561 μmol.min^-1.mg protein^-1, respectively. The temperature and pH optimum for purified peroxidase were 45℃ and pH 6.0, respective. However, it was stable at 30-60℃ and pH 4.0-8.0. The presence of metal ions such as Cu2＋ and Ca2＋ enhanced peroxidase activity. On the other hand, Cr3＋ and Hg2＋ strongly inhibited the enzyme activity at 500 p.M. Sodium dodecyl sulfate reduced a half of peroxidase activity at approximately 3 mM. Ivy gourd was stability in the presence of each urea concentrations. The affinity of the enzyme with different substrates showed as the highest relative activities on gallic acid followed by catechin, ascorbic acid and caffeic acid, respectively.
基金supported by the Finnish Centre of Excellence in Plant Signal Research granted by the Academy of Finland(grant number 213509)
文摘Class Ⅲ secretable plant peroxidases occur as a large family of genes in plants with many functions and probable redundancy. In this review we are concentrating on the evidence we have on the catalysis of lignin polymerization by class Ⅲ plant peroxidases present in the apoplastic space in the xylem of trees. Some evidence exists on the specificity of peroxidase isozymes in lignin polymerization through substrate specificity studies, from antisense mutants in tobacco and poplar and from tissue and cell culture lines of Norway spruce （Picea abies） and Zinnia elegans. In addition, real time （RT-）PCR results have pointed out that many peroxidases have tissue specific expression patterns in Norway spruce. Through combining information on catalytic properties of the enzymes, on the expression patterns of the corresponding genes, and on the presence of monolignols and hydrogen peroxide in the apoplastic space, we can show that specific peroxidases catalyze lignin polymerization in the apoplastic space of Norway spruce xylem.
