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Acetic acid esterase (EC 3.1.1.6) cleaves the acetyl groups substituted at O-2/O-3 of the xylan backbone of arabinoxylans and is known to modulate their functional properties. To date, this enzyme from cereals has not received much attention. In the present study, acetic acid esterase from 72 h ragi malt was isolated and purified to apparent homogeneity by a four-step purification, i.e., ammonium sulfate precipitation, DEAE-cellulose, Sephacryl S-200, and phenyl-Sepharose column chromatography, with a recovery of 0.36% and a fold purification of 34. The products liberated from alpha-NA and PNPA by the action of purified ragi acetic acid esterase were authenticated by ESI-MS and 1H NMR. The pH and temperature optima of the enzyme were found to be 7.5 and 45 degrees C, respectively. The enzyme is stable in the pH range of 6.0-9.0 and temperature range of 30-40 degrees C. The activation energy of the enzymatic reaction was found to be 7.29 kJ mol-1. The apparent Km and Vmax of the purified acetic acid esterase for alpha-NA were 0.04 microM and 0.175 microM min-1 mL-1, respectively. The molecular weight of the native enzyme was found to be 79.4 kDa by GPC whereas the denatured enzyme was found to be 19.7 kDa on SDS, indicating it to be a tetramer. EDTA, citric acid, and metal ions such as Fe+3 and Cu+2 increased the activity while Ni+2, Ca+2, Co+2, Ba+2, Mg+2, Mn+2, Zn+2, and Al+3 reduced the activity. Group-specific reagents such as eserine and PCMB at 25 mM concentration completely inhibited the enzyme while iodoacetamide did not have any effect. Eserine was found to be a competitive inhibitor. 相似文献
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Kumar KR Li L Yan M Bhaskarabhatla M Mobley AB Nguyen C Mooney JM Schatzle JD Wakeland EK Mohan C 《Science (New York, N.Y.)》2006,312(5780):1665-1669
The susceptibility locus for the autoimmune disease lupus on murine chromosome 1, Sle1z/Sle1bz, and the orthologous human locus are associated with production of autoantibody to chromatin. We report that the presence of Sle1z/Sle1bz impairs B cell anergy, receptor revision, and deletion. Members of the SLAM costimulatory molecule family constitute prime candidates for Sle1bz, among which the Ly108.1 isoform of the Ly108 gene was most highly expressed in immature B cells from lupus-prone B6.Sle1z mice. The normal Ly108.2 allele, but not the lupus-associated Ly108.1 allele, was found to sensitize immature B cells to deletion and RAG reexpression. As a potential regulator of tolerance checkpoints, Ly108 may censor self-reactive B cells, hence safeguarding against autoimmunity. 相似文献
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A pentabrominated phenolic diphenyl ether (1) that has not previously been reported from marine sources has been isolated from Dysidea herbacea collected at Pelorus Island, Great Barrier Reef, Australia. The structure was determined by comparison of NMR data with those of known structurally-related metabolites. NMR spectral assignments for (1) are discussed in context with those of three previously reported isomeric pentabrominated phenolic diphenyl ethers. 相似文献
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Allipuram Srinivas Pasupuleti Surendra Babu Ghattamaraju Maruthi Sankar Adusimilli Madhavi Gollapalli Eswara Chandra Vidyasagar 《Communications in Soil Science and Plant Analysis》2018,49(12):1502-1521
A study was conducted at Hyderabad during 2009–11 to determine phosphorus (P) dose for rice–rice and rice–sunflower. Available P increased when 100% recommended P dose (RDP) was applied. P applied to rice gave at par yield under 100 or 75% RDP. In rice–rice, grain yield of 5668 and 5775 kg ha?1 in kharif (5654 and 5760 kg ha?1 in rabi) were attained with P@75 and 100% RDP. Kharif P residual effect in rabi affected rice yield. P@100/75% RDP in kharif and rabi gave grain of 5916/5973 and straw 6230/6673 kg ha?1. P applied to sunflower revealed that yield was similar with 100 or 75% RDP. Sunflower yield was at par with P@100 or 75% RDP. 25% RDP in rice and sunflower may be reduced to attain similar yield of 100% RDP. In rice–rice, grain yield attained by 100% RDP in both seasons was 11.42t ha?1 yr?1, while 75% RDP gave yield of 11.45t ha?1yr?1. 相似文献
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Purification and characterization of ferulic acid esterase from malted finger millet (Eleusine coracana, Indaf-15) 总被引：2，自引：0，他引：2
Latha GM Srinivas P Muralikrishna G 《Journal of agricultural and food chemistry》2007,55(23):9704-9712
Ferulic acid esterase (EC 3.1.1.73) cleaves the feruloyl groups substituted at the 5'-OH group of arabinosyl residues of arabinoxylans and is known to modulate their functional properties. In this study, ferulic acid esterase from 96 h finger millet malt was purified to apparent homogeneity by three-step purification with a recovery of 3% and a fold purification of 22. The substrate p-nitrophenylferulate (PNPF) was synthesized and used to assay this enzyme spectrophotometrically. The products liberated from ragi and wheat water-soluble polysaccharides by the action of purified ragi ferulic acid esterase were identified by ESI-MS. The pH and temperature optima of the enzyme were found to be 6.0 and 45 degrees C, respectively. The pH and temperature stabilities of the enzyme were found to be in the range of 5.5-9.0 and 30 degrees C, respectively. The activation energy of the enzymatic reaction was found to be 4.08 kJ mol(-1). The apparent K m and V max of the purified ferulic acid esterase for PNPF were 0.053 microM and 0.085 unit mL(-1), respectively. The enzyme is a monomer with a molecular mass of 16.5 kDa. Metal ions such as Ni(2+), Zn(2+), Co(2+), and Cu(2+) and oxalic and citric acids enhanced the enzyme activity. The enzyme was completely inhibited by Fe(3+). Group specific reagents such as p-chloromercuric benzoate and iodoacetamide inhibited the enzyme, indicating the possible presence of cysteine residues in the active site pocket. 相似文献
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Sesha Srinivas Vutukuru Suma Chintada K. Radha Madhavi J. Venkateswara Rao Y. Anjaneyulu 《Fish physiology and biochemistry》2006,32(3):221-229
Static-renewal bioassays [Methods for acute toxicity tests with fish, macro-invertebrates and amphibians: USEPA, ERS, EPA 660/3 75-009 (1975)] were carried out on Esomus danricus exposed to sub-lethal (0.55 mg/l) and lethal (5.5 mg/l) concentrations of copper. The 96-h median lethal concentration (LC50) was 5.5 mg/l. Biochemical stress responses, such as visceral superoxide dismutase (SOD) and catalase (CAT) activities, were measured during this 96-h period. Malondialdehyde, a product of lipid peroxidation, was present at elevated levels in the visceral tissue of copper-exposed fish. Copper was found to be highly toxic to the fish and induced significant declines (p < 0.05–0.001) in all of the biochemical profiles studied, demonstrating a linear and positive correlation with both the concentration and duration of exposure to copper. In E. danricus, CAT appeared to be more sensitive to copper exposure (p < 0.001) than SOD at both lethal and sub-lethal levels. These results indicate that antioxidant responses can be employed as biomarkers of oxidative stress for this species in aquatic environments contaminated with copper. 相似文献
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Kripa KG Sangeetha R Madhavi P Deepthi P 《Pakistan journal of biological sciences: PJBS》2011,14(19):894-899
This study was proposed based on the folklore claim and on the scarcity of scientific evidence from the literature for the medicinal uses of Breynia retusa. The aim of the present study was to analyse the phytochemical constituents of the leaves of B. retusa. The fractions obtained by successive fractionation using solvents of varying polarity were studied for the presence of primary and secondary metabolites and the total phenolic content of the different fractions were determined by HPLC. The results of the study support the traditional acclaim of the therapeutic uses of B. retusa. The potential of B. retusa to inhibit alpha-amylase, a prime enzyme involved in carbohydrate metabolism was analysed and it was observed that the ethyl acetate and methanolic extract of the leaves of B. retusa possessed in vitro amylase inhibitory activity. 相似文献