Biosynthesis of halogenated monoterpenes in Plocamium cartilagineum

The biosynthesis of halogenated monoterpenes in this alga has been studied by feeding experiments using labelled bicarbonate, acetate and mevalonate. Seasonal effects have been observed in these studies and the incorporation of H¹⁴CO₃^? into primary metabolites is consistent with the expected reductive pentose pathway. The incorporations of [³H, ¹⁴C]mevalonates and limited chemical degradations are consistent with the expected cyclization to these rearranged monoterpenes. Attempts to obtain cell free systems to carry out all or part of the biosynthetic sequence or to halogenate various substrates have been unsuccessful, although a classical peroxidase has been isolated, characterized and partially purified.     

Changes in Composition of Soluble Intercellular Proteins Isolated from Healthy and TMV-Infected Nicotiana tabacum L. cv. Xanthi-nc

Changes in ribonucleases (RNases), phosphomonoesterase (PME), phosphodiesterase (PDE), glucose-6-phosphate dehydrogenase (G6P DH), polyphenoloxidases, peroxidases and proteases activity and PR-proteins composition in leaf tissue and intercellular fluid (ICF) isolated from leaf tissue of healthy and TMV-infected hypersensitive tobacco (Nicotiana tabacum L. cv. Xanthi-nc) plants (non-inoculated leaves) were studied. The amount of the proteins and the enzymes of intercellular space was less than 3 % of the total amount of proteins and the enzymes found in homogenate of healthy leaves. The TMV infection did not significantly change this observation. The great increase in the activities of the enzymes was observed in homogenates of the infected leaves, especially of the enzymes involved in biosynthesis of precursors needed for virus multiplication (G6P DH, RNase, PME, PDE). This is in contrast with the activities of the enzymes of ICF, which were only partly increased. The ICF proteins of infected plants were separated by means of ion exchange chromatography on DEAE cellulose. The isozymes of peroxidase, polyphenoloxidase, PME and PDE were identified. Using discontinuous nondenaturating polyacrylamide gel electrophoresis of DEAE cellulose fractions, the detection of isozymes of peroxidases and PR-proteins was performed. By means of SDS-PAGE the molecular masses of PR-proteins were identified: 15 – 16 kDa (group 1), 27 – 28 kDa (group 3: chitinases) and 36 – 40 kDa (group 2a: -1,3-glucanases).     

Developmental Histology of Organogenic and Embryogenic Tissue in Picea omorika Culture

Newly synthesized derivatives of α-aminoalkanephosphonic acids (aminophosphonates) differ in the substituents at the carbon, nitrogen, and phosphorus atoms. They modified in different degree the properties of cucumber (Cucumis sativus cv. Wisconsin) cotyledon membranes, physiological activity of some enzymes (guaiacol and pyrogallol peroxidases, and catalase), chlorophyll content, and cellular membrane lipid peroxidation. Most active modifiers were those possessing sufficiently long hydrocarbon substituents at the nitrogen atom (C₁₀H₂₁) or isopropyl chain at the phosphorus atom. The branched tertbutyl group at the carbon atom enhanced slightly the activities of peroxidases in contrast to hexane ring at the same position, which decreased them. This revised version was published online in July 2006 with corrections to the Cover Date.     

Regioselective nitration of phenol induced by catalytic antibodies

Catalytic antibodies with a metalloporphyrin cofactor represent a new generation of biocatalysts tailored for selective oxidations. Thus monoclonal antibodies, 3A3, were raised against microperoxidase 8 (MP8), and the corresponding 3A3-MP8 complexes were shown previously to have a high peroxidase activity. This paper shows that those complexes also catalyzed efficiently the nitration of phenol into 2- and 4-nitrophenol by NO₂ ^– in the presence of H₂O₂. pH dependence studies suggested that no amino acid from the antibody protein participated in the heterolytic cleavage of the O-O bond of H₂O₂. The inhibition of the reaction by cyanide and radical scavengers suggested a MP8-mediated peroxidase-like mechanism, involving the reduction of high-valent iron-oxo species by NO₂ ^– and phenol producing, respectively, NO₂ · and phenoxy radicals, which then reacted to give nitrophenols. Finally, the antibody protein appears to have two major roles: (i) it protects MP8 toward oxidative degradations and (ii) it induces a regioselectivity of the reaction toward the formation of 2-nitrophenol.     

Decolourisation of anthraquinone-and anthracene-type dyes by versatile peroxidases from bjerkandera fumosa and pleurotus ostreatus D1

The catalytic properties of a versatile peroxidase from Pleurotus ostreatus D1 (Jacquin) P. Kummer were studied in comparison with that of a typical versatile peroxidase from Bjerkandera fumosa 137 (Per.:Fr) Karst. Decolourisation activities of both enzymes towards a wide range of dyes containing condensed aromatic rings (anthraquinone- and anthracene-type) were found. The anthraquinone dyes were decolourised rapidly by both tested peroxidases. The presence of polymerisation reaction products of Acid Blue 62, Basic Blue 22 and Reactive Blue 4 oxidation, and breakdown of aromatic rings of Alizarin Red were observed. The main catalytic constants (KM and Vmax) of the decolourisation reactions of anthraquinone dyes were calculated. In the case of Alizarin Red, inhibition of the activity of versatile peroxidase from P. ostreatus D1 by an excess of the substrate was observed. Independence from Mn²⁺ ions of the catalytic activity of versatile peroxidase from P. ostreatus D1 towards different substrates was revealed. Finally, differences in the catalytic activity towards anthracene-type dyes and monoaromatic substrates of both peroxidases were found.     

^60Coγ辐射对亚洲玉米螟体内保护酶活力的影响

作研究了亚洲玉米螟Ostrinia furnacalis(Guen．)不同虫态(3～4龄幼虫、1～2d龄蛹、当天羽化成虫)体内过氧化物醇(POD)和过氧化氢醇(CAT)活力在不同^60Coγ辐照条件下的变化。结果表明：亚洲玉米螟不同虫杰的POD活力顺序为;雌成虫>1～2d蛹>雄成虫>3～4龄幼虫;CAT活力为：3～4龄幼虫>雄成虫>雌成虫>1～2d龄蛹。辐照处理后,POD活力随辐照剂量的增加而呈上升趋势,三种虫态均以40Krad处理后曲活力最高;CAT的话力变化较大．3～4龄幼虫、1～2d龄蛹和雄威虫都以30Krad处理曲活力最高,雌戚虫以20Krad处理的最高。本试验结果有助于阐明辐射对昆虫生理生化的效应。     

Glucose exerts a negative effect over a peroxidase from <Emphasis Type="Italic">Trichosporon asahii</Emphasis>, with carotenoid cleaving activity

Tobacco aroma compounds were generated via lutein cleavage by the combined action of a yeast and a bacterium identified as Trichosporon asahii and Paenibacillus amylolyticus, respectively. In this study, an inverse relationship between glucose concentration and the generation of three compounds, present in the tobacco aroma profile, was observed in mixed cultures. In order to identify the organism sensitive to the sugar effect, both were grown separately. The presence of glucose suppressed β-ionone production by T. asahii grown with lutein. However, the biotransformation of the ionone into its reduced derivatives (7,8-dihydro-β-ionone and 7,8-dihydro-β-ionol) by P. amylolyticus was not affected by the sugar . This pointed to the cleavage of lutein, a step within the process necessary for the synthesis of β-ionone, as the target of the glucose effect. In vitro studies with crude extracts and concentrated cell-free medium derived from T. asahii cultures showed that the carotenoid breakdown activity was located extracellularly and only detected in supernatants from yeast cells grown in the absence of the sugar. Rather than an inhibition or a mechanism affecting the enzyme secretion, the glucose effect on lutein degradation comprised another regulatory level. Further experiments showed that the enzyme responsible for lutein breakdown and susceptible to the sugar effect exhibited a high degree of identity to fungal peroxidases, studied as well, for their involvement in carotenoid cleavage.     

The role of jasmonic acid in root mitochondria disruption

Methyl jasmonate (MeJA) produces an important reduction in the accumulation of proteins related to energy metabolism. The treatment of hairy roots (HR) with MeJA increased the accumulation of H₂O₂ during the first 48 h and this H₂O₂ accumulation was also observed in isolated mitochondria. Peroxidase and catalase activities decreased in the presence of MeJA, and this decrease directly correlated with the increase of H₂O₂ in HR treated with MeJA. This suggests that the H₂O₂ burst due to MeJA is the initial response to mitochondria disruption in the roots.