A highly stable cambialistic-superoxide dismutase from Antrodia camphorata: Expression in yeast and enzyme properties

Functional characterization of a manganese superoxide dismutase from Avicennia marina: insights into its role in salt, hydrogen peroxide, and heavy metal tolerance

Avicennia marina is a salt-tolerance plant with high antioxidant and antibacterial potential. In the present work, a gene encoding MnSOD from Avicennia marina (AmSOD2) was cloned in the expression vectors pET28a. The resulting constructs were transformed into Escherichia coli strains Rosetta (DE3). Following the induction with Isopropyl β-D-1-thiogalactopyranoside, the protein His-AmSOD2 was expressed but dominantly found in the insoluble fraction of strain R-AmSOD2. Due to detection of mitochondrial transit peptide in the amino acid sequence of AmSOD2, the transit peptide was removed and AmSOD2 without transit peptide (tAmSOD2) was expressed in E. coli and dominantly found in the soluble fraction. The enzyme His-tAmSOD2 exhibited a molecular mass of 116 kDa in native condition. Nevertheless, in reducing conditions the molecular mass is 28 kDa indicating the enzyme His-tAmSOD2 is a tetramer protein. As shown by ICP analysis there is one mole Mn2+ in each monomer. The Pure His-tAmSOD2 was highly active in vitro, however the activity was almost three-fold lower than His-AmSOD1. Whereas the high stability of the recombinant His-AmSOD1was previously shown after incubation in a broad range pH and high temperature, His-tAmSOD2 was stable up to 50 °C and pH 6 for 1 h. The gene expression analysis showed that the gene encoding AmSOD2 is expressed in root, shoot and leaves of A. marina. In addition, the results show that the expression in the leaves was enhanced after treatment of plant with NaCl, H2O2, Cd2+ and Ni2+ indicating the important role of MnSOD in the resistant mechanism of mangroves.

Biochemical characterization of a functional recombinant aryl-alcohol dehydrogenase from Taiwanofungus camphorata

BACKGROUND

Aryl-alcohol dehydrogenases (AADs) have been known to involve in the metabolism of aromatic compounds.

RESULTS

One TcAAD cDNA (GenBank HQ453361) encoding a putative aryl-alcohol dehydrogenase (AAD) was cloned from Taiwanofungus camphorata. The deduced amino acid sequence is conserved among the reported AADs. A 3-D structural model of the TcAAD has been created based on the known structure of voltage-dependent potassium channels subunit beta-2 (PDB code: 3EAU). To characterize the TcAAD, the coding region was subcloned into an expression vector and transformed into Saccharomyces cerevisiae. The recombinant His6-tagged TcAAD was overexpressed and purified by Ni affinity chromatography. The purified enzyme showed a band of approximately 39 kDa on a 12% SDS-PAGE. The molecular mass determined by MALDI-TOF is 40.58 kDa which suggests that the purified enzyme is a monomeric enzyme. Using veratraldehyde as a substrate, the K_M, V_max of TcADD was determined at pH 6.0. Using benzyl alcohol derivatives as substrates, the oxidizing power of TcADD via NAD⁺ at pH 9.6 was studied.

CONCLUSIONS

The coding sequence of the TcAAD cDNA was introduced into an S. cerevisiae expression system and the active enzyme purified and characterized. Understanding the properties of this TcAAD will be beneficial for its potential in xenobiotic detoxification or production of natural flavors.

Modulation of nitrosative stress via glutathione-dependent formaldehyde dehydrogenase and S-nitrosoglutathione reductase

Glutathione-dependent formaldehyde dehydrogenase (GFD) from Taiwanofungus camphorata plays important roles in formaldehyde detoxification and antioxidation. The enzyme is bifunctional. In addition to the GFD activity, it also functions as an effective S-nitrosoglutathione reductase (GSNOR) against nitrosative stress. We investigated the modulation of HEK (human embryonic kidney) 293T cells under nitrosative stress by transfecting a codon optimized GFD cDNA from Taiwanofungus camphorata (Tc-GFD-O) to these cells. The parental and transfected HEK 293T cells were then subjected to S-nitrosoglutathione treatment to induce nitrosative stress. The results showed that in Tc-GFD-O-transfected 293T cells, the expression and activity of GFD increased. Additionally, these cells under the nitrosative stress induced by S-nitrosoglutathione showed both higher viability and less apoptosis than the parental 293T cells. This finding suggests that the Tc-GFD-O in HEK 293T cells may provide a protective function under nitrosative stress.

Antrodia cinnamomea profoundly exalted the reversion of activated hepatic stellate cells by the alteration of cellular proteins

The direct modulation of Antrodia cinnamomea (AC) on the prominent role of liver fibrosis-hepatic stellate cells (HSCs) in situ remains unclear. Firstly, the administration of A. cinnamomea mycelial extract (ACME) could improve liver morphology and histological changes including collagen formation and GPT activity in the liver of thioacetamide (TAA)-injured rats. The morphology and fatty acid restore of TAA-induced HSCs (THSCs) returned to the non-chemical induced HSCs (NHSCs) type as measured by immunofluorescence and Oil Red O staining. PPARγ was upregulated associated with the lowering of α-SMA protein in NHSC-ACME. ACME inhibited the MMP-2 activity in NHSCs by gelatin Zymography. After LC-MS/MS, the cytoskeleton (tubulin, lamin A) and heat shock protein 8 in NHSC-ACME, and guanylate kinase, brain-specific kinase, SG-II and p55 proteins were downregulated in THSC-ACME. Whereas MHC class II, SMC6 protein, and phospholipase D were upregulated in NHSC-ACME. Furthermore, PKG-1 was downregulated in NHSC-ACME and upregulated in THSC-ACME. SG-II and p55 proteins were downregulated in NHSC-ACME and THSC-ACME by Western blotting. Taken together, the beneficial effect of A. cinnamomea on the induction of HSC cellular proteins is potentially applied as an alternative and complementary medicine for the prevention and amelioration of a liver injury.

Role of 5-aminolevulinic acid in the salinity stress response of the seeds and seedlings of the medicinal plant Cassia obtusifolia L

BACKGROUND

Soil salinity, one of the major abiotic stresses affecting germination, crop growth, and productivity, is a common adverse environmental factor. The possibility of enhancing the salinity stress tolerance of Cassia obtusifolia L. seeds and seedlings by the exogenous application of 5-aminolevulinic acid (ALA) was investigated.

RESULT

To improve the salinity tolerance of seeds, ALA was applied in various concentrations (5, 10, 15, and 20 mg/L). To improve the salinity tolerance of seedlings, ALA was applied in various concentrations (10, 25, 50, and 100 mg/L). After 10 mg/L ALA treatment, physiological indices of seed germination (i.e., germination vigor, germination rate, germination index, and vigor index) significantly improved. At 25 mg/L ALA, there was a significant protection against salinity stress compared with non-ALA-treated seedlings. Chlorophyll content, total soluble sugars, free proline, and soluble protein contents were significantly enhanced. Increased thiobarbituric acid reactive species and membrane permeability levels were also inhibited with the ALA treatment. With the treatments of ALA, the levels of chlorophyll fluorescence parameters, i.e., the photochemical efficiency of photosystem II (F_v/F_m), photochemical efficiency (F_v'/F_m'), PSII actual photochemical efficiency (ΦPSII), and photochemical quench coefficient (qP), all significantly increased. In contrast, the non-photochemical quenching coefficient (NPQ) decreased. ALA treatment also enhanced the activities of superoxide dismutase, peroxidase, and catalase in seedling leaves. The highest salinity tolerance was obtained at 25 mg/L ALA treatment.

CONCLUSION

The plant growth regulator ALA could be effectively used to protect C. obtusifolia seeds and seedlings from the damaging effects of salinity stress without adversely affecting plant growth.

A peroxiredoxin cDNA from Taiwanofungus camphorata: role of Cys31 in dimerization

Peroxiredoxins (Prxs) play important roles in antioxidant defense and redox signaling pathways. A Prx isozyme cDNA (TcPrx2, 745 bp, EF552425) was cloned from Taiwanofungus camphorata and its recombinant protein was overexpressed. The purified protein was shown to exist predominantly as a dimer by sodium dodecyl sulfate-polyacrylamide gel electrolysis in the absence of a reducing agent. The protein in its dimeric form showed no detectable Prx activity. However, the protein showed increased Prx activity with increasing dithiothreitol concentration which correlates with dissociation of the dimer into monomer. The TcPrx2 contains two Cys residues. The Cys(60) located in the conserved active site is the putative active peroxidatic Cys. The role of Cys(31) was investigated by site-directed mutagenesis. The C31S mutant (C(31) → S(31)) exists predominantly as a monomer with noticeable Prx activity. The Prx activity of the mutant was higher than that of the corresponding wild-type protein by nearly twofold at 12 μg/mL. The substrate preference of the mutant was H2O2 > cumene peroxide > t-butyl peroxide. The Michaelis constant (K M) value for H2O2 of the mutant was 0.11 mM. The mutant enzyme was active under a broad pH range from 6 to 10. The results suggest a role of Cys(31) in dimerization of the TcPrx2, a role which, at least in part, may be involved in determining the activity of Prx. The C(31) residue does not function as a resolving Cys and therefore the TcPrx2 must follow the reaction mechanism of 1-Cys Prx. This TcPrx2 represents a new isoform of Prx family.

Monothiol glutaredoxin cDNA from Taiwanofungus camphorata: a novel CGFS-type glutaredoxin possessing glutathione reductase activity

Glutaredoxins (Grxs) play important roles in the redox system via reduced glutathione as a reductant. A TcmonoGrx cDNA (1039 bp, EU158772) encoding a putative monothiol Grx was cloned from Taiwanofungus camphorata (formerly named Antrodia camphorata). The deduced amino acid sequence is conserved among the reported monothiol Grxs. Two 3-D homology structures of the TcmonoGrx based on known structures of human Grx3 (pdb: 2DIY_A) and Mus musculus Grx3 (pdb: 1WIK_A) have been created. To characterize the TcmonoGrx protein, the coding region was subcloned into an expression vector pET-20b(+) and transformed into E. coli C41(DE3). The recombinant His6-tagged TcmonoGrx was overexpressed and purified by Ni(2+)-nitrilotriacetic acid Sepharose. The purified enzyme showed a predominant band on 10% sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme exhibited glutathione reductase (GR) activity via dithionitrobenzoate (DTNB) assay. The Michaelis constant (K(M)) values for GSSG and NADPH were 0.064 and 0.041 mM, respectively. The enzyme's half-life of deactivation at 60 °C was 10.5 min, and its thermal inactivation rate constant (k(d)) was 5.37 × 10(-2) min(-1). The enzyme was active under a broad pH range from 6 to 8. The enzyme retained 50% activity after trypsin digestion at 37 °C for 40 min. Both mutants C(40)→S(40) and C(165)→S(165) lost 40-50% GR activity, whereas the mutant S(168)→C(168) showed a 20% increase in its GR activity.

The role of 5-aminolevulinic acid in the response to cold stress in soybean plants

In this study, the possibility of enhancing cold stress tolerance of soybean plants (Glycine max L.) by exogenous application of 5-aminolevulinic acid (ALA) was investigated. ALA was added to the Hoagland solution at various concentrations ranging from 0 to 40 μM for 12 h. After ALA treatment, the plants were subjected to cold stress at 4°C for 48 h. ALA at low concentrations (5-10 μM) provided significant protection against cold stress compared to non-ALA-treated plants, enhancing chlorophyll content (Chl) as well as relative water content (RWC). Increase of thiobarbituric acid reactive species (TBARS) levels was also prevented, whereas exposure to higher ALA concentrations (15-40 μM) brought about a dose dependent increase of these species, reaching a maximum of 117% in plants pre-treated with 40 μM ALA compared to controls. ALA pre-treatment also enhanced catalase (CAT) and heme oxygenase-1 (HO-1) activities. These findings indicate that HO-1 acts not only as the rate limiting enzyme in heme catabolism, but also as an antioxidant enzyme. The highest cold tolerance was obtained with 5 μM ALA pre-treatment. Results show that ALA, which is considered as an endogenous plant growth regulator, could be used effectively to protect soybean plants from the damaging effects of cold stress by enhancing the activity of heme proteins, e.g., catalase (CAT) and by promoting heme catabolism leading to the production of the highly antioxidant biliverdin and carbon monoxide, without any adverse effect on the plant growth.

Cloning, expression, and characterization of a thioredoxin reductase cDNA from Taiwanofungus camphorata

A cDNA encoding putative thioredoxin reductase (TR) was identified from a medicinal mushroom, Taiwanofungus camphorata (T. camphorata). Alignment of the deduced amino acid sequence with TRs from other organisms showed high levels of identity (59-74%). A three-dimensional (3-D) homology structure was created for this TR. Functional T. camphorata TR (TcTR) was overexpressed in yeast and purified. The purified enzyme showed a monomic form on a 10% sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme's half-life of deactivation at 60 degrees C was 12.9 min, and its thermal inactivation rate constant K(d) was 5.37 x 10(-2) min(-1). The optimal pH for the enzyme was pH 8 and retained about 76% activity in the presence of 0.1 M imidazole. The enzyme showed 50% activity after 10 min of incubation at 37 degrees C with chymotrypsin. The Michaelis constant (K(m)) value for dithionitrobenzoate (DTNB) was 1.59 mM.

Effects of long-term chilling on ultrastructure and antioxidant activity in leaves of two cucumber cultivars under low light

Cucumber (Cucumis sativus L.) cv. Xintaimici (a chilling-resistant cultivar) and cv. Jinyan no. 4 (a chilling-sensitive cultivar) were subjected to two temperatures (15/15 and 25/18 degrees C) under low light (100 mumol m(-2) s(-1)) to understand the relationship between ultrastructural changes and the antioxidant abilities caused by low temperature (15/15 degrees C). We also aimed to find indicators for chilling resistance that could be used on a routine basis in breeding programs of greenhouse crops. At the 15/15 degrees C treatment, the membranes of chloroplast, mitochondrion, ER and plasma were not significantly changed in Xintaimici, whereas they were seriously affected in Jinyan no. 4. This result was consistent with the changes of malonaldehyde in chilling-stressed cucumber leaves. The antioxidant activities were changed under low temperature according to cultivar-expected resistance, relating in part to the described ultrastructural changes. The activities of superoxide dismutase (EC 1.15.1.1) and guaiacol peroxidase (EC 1.11.1.7) increased in chilling-stressed leaves of both cultivars, but the two enzymes were not responsible for the difference between cucumber cultivars. At 15/15 degrees C, contents of GSH and activities of glutathione reductase (GR, EC 1.6.4.2) increased more in leaves of Xintaimici than in those of Jinyan no. 4, while catalase (CAT, EC 1.11.1.6) activities decreased less. GSH, GR and CAT were affected by low temperature and cultivars and correlated with the difference in ultrastructure between chilling-stressed cucumber cultivars. We propose that the three antioxidants might be therefore used as biochemical indicators to screen chilling-resistant cucumber cultivars.