Synthetic auxin, naphthaleneacetic acid ( NAA ), promoted rooting in soybean ( Glycine max ) hypocotyls. The activities of anionic peroxidases (PODs, pI 3.5 and pI 3.7 ) and cationic PODs ( pI 8.3, pI 9.1 and pI 9.4 ) in soybean hypocotyls were significantly inhibited by exogenous NAA during the induction of adventitious roots. In addition, the reduction in the activity of PODs ( pI 4.4, pI 8.3 and pI 9.4 ) were correlated with a reduction of their corresponding transcription activity. The PODs patterns and transcription in the NAA-treated hypocotyls demonstrated the specific effect of NAA on POD ioszymes, indicating that NAA might suppress PODs genes expression during the adventitious root formation. The decline of PODs activity in the NAA-treated hypocotyls was accompanied by the decrease of lignin contents. We suggest that both of anionic and cationic PODs might be in part responsible for lignin synthesis in soybean hypocotyls.

The significant root inhibition of growth in Cd-treated soybean (Glycine max) seedling correlated with the increase of H2O2 levels, PODs and laccases activity. The increase of the activities of PODs (pI 8.8, pI 7.7, pI 5.2, pI 4.5, pI 4.4 and pI 3.7) and laccases (pI 9.2, pI 8.9 and pI 8.3, pI 5.4, pI 4.2 and pI 3.7) are accompanied by a rise of lignin contents in Cd-treated tissues. Our results suggested that laccases work during the early stage of Cd treatment. Laccases and peroxidases work cooperatively in lignin synthesis when the time of Cd treatment was prolonged.

In our study, the decrease of H2O2 levels in wounding-treated tissues of soybean ( Glycine Max ) hypocotyls is accompanied by the enhancement of the POD activity. The POD activity was significantly enhanced 0.5 d after wounding treatment. The laccase activity was significantly enhanced 1-2 d after wounding treatment. The enhancement of POD by mechanical wounding occurred a day earlier than laccase. The increase in activities of POD and laccase is correlated with a rise in lignin contents in wounding-treated tissues. We suggest that in control tissues, laccase might play major role on the lignin biosynthesis, hence, POD by utilizing H2O2 play the major role on the lignin biosynthesis during the wounding process.

Harpinpss, a pathogenic protein, encoded by hrpZ in the hrp gene cluster from Pswudomonas syringae pv. syringae, can induce the hypersensitive response in tobacco (Nicotiana tabacum L. cv. Xanthi). The lesion area on the tobacco leaves was visible 6 h after inoculation with harpin, and was evident 12 h after inoculation. The lignin content in harpin-treated tobacco leaves was about 2.5-fold as compared with the controls 24 h after inoculation. There were six isozymes of POD (pI 9.5, pI 8.7, pI 5.3, pI 4.4, pI 3.7, and pI 3.5) and seven isozymes of laccase (pI 9.4, pI 8.6, pI 7.8, pI 5.4, pI 4.5, pI 3.8, and pI 3.6) identified by isoelectric point in extracts of harpin-inoculated tobacco leaves. POD isozymes (pI 4.4, pI 5.3 and pI 8.7) and laccase isozyme (pI 7.8) only appeared in harpin-inoculated tissues. The increased POD isozymes (pI 4.4, pI 8.7, pI 9.5) are correlated with the rise of transcripts of these enzymes confirmed by the method of reverse transcriptase-polymerase chain reaction (RT-PCR).

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 91-100).

Schistosoma mansoni and Fasciola hepatica are parasitic trematodes which contain cytochrome c peroxidase (CcP) in their mitochondria, an enzyme that is absent in mammalian tissues. CcP reduces hydrogen peroxide to H2O using cytochrome c as the electron donor. Both parasites are catalase deficient; thus, cytochrome c peroxidase and glutathione peroxidase are the enzymes involved in the detoxification of H2O 2 in these organisms. The enzymatic activity of these two peroxidases may enable S. mansoni and F. hepatica to survive oxidative stress. The main objective of this study was to characterize cytochrome c peroxidase from S. mansoni and F. hepatica . Kinetic studies of this enzyme in crude homogenate and isolated mitochondria of S. mansoni were initially performed, followed by purification studies from S. mansoni and F. hepatica . The parasite enzyme has affinity for horse heart and yeast cytochrome c and it is inhibited by sodium azide and potassium cyanide. CcP was purified close to homogeneity and identified as a protein containing heme. The antioxidant capability of F. hepatica CcP was tested in vitro , demonstrating that CcP protected the sugar deoxyribose from oxidative degradation. Exposure of adult worms to H2O2 caused a decrease in S. mansoni CcP activity in vivo. An attempt was made to clone the S. mansoni CcP gene. The experiments did not result in the cloning of the CcP gene, but led to the identification and cloning of another protein, a component of a cytosolic chaperonin, t-complex polypeptide one (TCP-1). TCP-1 from S. mansoni is highly homologous to TCP-1 proteins from different organisms including, Chinese hamster, human, Drosophila and yeast and carries ATP binding amino acid motifs indicating that it has ATPase activity.

Persistent organic pollutants and heavy metals are released into the environment through different anthropogenic processes. They are of concern because they tend to bioaccumulate in the food chain and show adverse health effects ranging from acute to chronic toxicity. These pollutants need therefore to be monitored to conserve the environment. Conventionally, samples are sent to a laboratory for analysis by standard techniques such as chromatography and spectroscopy. Although these conventional techniques display high accuracy and low detection limits, they are expensive, require the use of highly trained personnel and tedious sample preparation. In comparison, electrochemical methods such as biosensors are sensitive, low cost and simple to operate. In this thesis, the determination of selected persistent organic pollutants (polybrominated diphenyl ethers, polybrominated biphenyls and polychlorinated biphenyls) and heavy metals (Cd, Pb and Cu) was achieved by the use of amperometric inhibition biosensor based on horseradish peroxidase (HRP) immobilized on the surface of platinum-polyaniline modified electrode. Polyaniline (PANI) film was electrochemically deposited on the platinum electrode surface. The film was characterized by cyclic voltammetry and spectrometric techniques. The CV results proved that the PANI was electroactive and exhibited a fast reversible electrochemistry. Characteristic Ultraviolet–Visible and Fourier Transform Infrared features of the polymer film were identified. They revealed that PANI film synthesized in this study is the conductive emeraldine salt. Horseradish peroxidase based biosensor was constructed by electrostatic attachment of the enzyme onto Pt-PANI electrode surface. Spectrometric and cyclic voltammetric results indicated that the immobilized HRP retained its bioelectrocatalytic activity towards the reduction of hydrogen peroxide. The Pt/PANI/HRP biosensor showed a linear response over a concentration range of 0.05 to 3.17 mM with a detection limit of 36.8 nM. Apparent Michaelis- Menten constant ( app M K ) was calculated as 1.04 mM. This implied that the HRP biosensor had a high affinity for H2O2. Furthermore, the fabricated biosensor showed high sensitivity, good reproducibility, repeatability and long-term stability. The Pt/PANI/HRP biosensor was applied to the determination of selected persistent organic pollutants and heavy metals. The latter was found to inhibit the HRP enzyme’s activity. The percentage inhibition of the investigated persistent organic pollutants decreases in the following order: 2,2´4,4´,6-pentabrominated diphenyl ether> 2-brominated biphenyl> 2-chlorinated biphenyl> 2,2´,4,5,5´-pentachlorinated biphenyl> 2,4,4´-trichlorinated biphenyl. In the case of heavy metals, the degree of inhibition of heavy metals was highest for Cd2+, followed by Cu2+ and then Pb2+. Kinetic study for the amperometric response to H2O2, recorded in the absence and presence of persistent organic pollutants and heavy metals revealed that for polybrominated diphenyl ethers, the inhibition process corresponded to a competitive type whereas for polybrominated biphenyls, polychlorinated biphenyls and heavy metals, it corresponded to the on-competitive type. The biosensor exhibited high sensitivity towards the determination of the metals and persistent organic pollutants as pollutants in real water samples, namely tap water and landfill leachate samples. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2010.

Thesis (Ph. D.)--University of Missouri--Columbia, 1998. / "July 1998." Typescript. Vita. Includes bibliographical references (leaves 138-170). Also available on the Internet.

Includes bibliographical references (p. 91-95).

Thesis (Ph. D.)--Institute of Paper Science and Technology, Georgia Institute of Technology, 2003. / Includes bibliography.