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151.
152.
Extracellular Enzyme Activity Associated with Degradation of Beech Wood in a Central European Stream
The degradation of beech wood (Fagus sylvatica L.) was followed over 16 months in a central European upland stream, the Breitenbach. 1 cm3 cubes of beech wood were placed on the stream bed and sampled at monthly intervals. Besides mass loss, fungal biomass (ergosterol content) and lignin content, the activity of two extracellular enzymes was measured: β‐D‐glucosidase, an enzyme involved in the degradation of cellulose, and phenoloxidase, a ligninolytic enzyme. The suitability of the fluorigenic model substrate methylumbelliferyl‐β‐D‐glucoside for measuring β‐D‐glucosidase activity in wood from aquatic environments was tested. This technique is much more sensitive than the conventional photometric method. The beech wood was degraded at a constant rate of k = 0.00272 d–1 across the entire 16‐month incubation period. There was a rapid onset of microbial colonisation, as witnessed by the initial detection of enzyme activity, after only 7 days of exposure. Lignin and ergosterol content as well as β‐glucosidase activity reached their highest values at the end of the 16‐month incubation period. Phenoloxidase activity increased rapidly to a maximum after 6 weeks, and then decreased to almost zero by the end of the experiment. The combination of biochemical techniques for measuring extracellular enzyme activities with measurements of mass loss, chemical composition and microbial colonisation provided valuable insights into the decomposition of wood in aquatic environments. 相似文献
153.
Joachim Stöckigt Santosh Panjikar Martin Ruppert Leif Barleben Xueyan Ma Elke Loris Marco Hill 《Phytochemistry Reviews》2007,6(1):15-34
The biosynthetic pathway leading to the monoterpenoid indole alkaloid ajmaline in Rauvolfia serpentiin serpentina is one of the most studied in the field of natural product biosynthesis. Ajmaline has a complex structure which is based
on a six-membered ring system harbouring nine chiral carbon atoms. There are about fifteen enzymes involved, including some
involving the side reactions of the ajmaline biosynthetic pathway. All enzymes exhibit pronounced substrate specificity. In
the recent years isolation and sequencing of their cDNAs has allowed a detailed sequence analysis and comparison with functionally
related and occasionally un-related enzymes. Site-directed mutations of several of the ajmaline-synthesizing enzymes have
been performed and their catalytic residues have been identified. Success with over-expression of the enzymes was an important
step for their crystallization and structural analysis by X-ray crystallography. Crystals with sufficient resolution were
obtained from the major enzymes of the pathway. Strictosidine synthase has a 3D-structure with a six-bladed β-propeller fold
the first time such a fold found in the plant kingdom. Its ligand complexes with tryptamine and secologanin, as well as structure-based
sequence alignment, indicate a possible evolutionary relationship to several primary sequence-unrelated structures with this
fold. The structure of strictosidine glucosidase was determined and its structure has as a (β/α)8 barrel fold. Vinorine synthase provides the first 3D structure of a member of BAHD enzyme super-family. Raucaffricine glucosidase
involved in a side-route of ajmaline biosynthesis has been crystallized. The ajmaline biosynthetic pathway is an outstanding
example where many enzymes 3D-structure have been known and where there is a real potential for protein engineering to yield
new alkaloid. 相似文献
154.
C. FREEMAN G. LISKA N.J. OSTLE M.A. LOCK S. HUGHES B. REYNOLDS J. HUDSON 《Biogeochemistry》1997,39(2):177-187
Possible interactions between soil enzymes and thebiogeochemistry of wetlands were investigated duringa field-based drought simulation. Under control(waterlogged) conditions, correlations were foundbetween the activity of the enzyme B-glucosidase andtwo properties associated with carbon cycling, namelyi) CH4 release r = 0.79,p lt 0.01) and ii) dissolvedorganic carbon concentration (r= -0.81, p lt 0.01). In contrast,the transition to drought conditions resulted in correlations betweenB-glucosidase activity and certain mineralisationprocesses, namely the release of mg and Ca(r = 0.72, p lt 0.05). Sulphataseactivity correlated with changes in sulphate concentration during the droughtsimulation (r = 0.73, p lt 0.05).Further support for the suggested enzymic involvement in biogeochemicalprocesses was found in laboratory studies. Theseexperiments indicated that increasing the abundance ofB-glucosidase could stimulate trace gas emissions(p lt 0.001) and increase the concentration ofmagnesium and calcium (p lt 0.05). Increasedsulphatase abundance caused a suppression of methane emissions(p = 0.053). 相似文献
155.
Sivasubramanian Suhitha Krishnaswamy Gunasekaran Devadasan Velmurugan 《Bioinformation》2012,8(23):1125-1131
Medicinal plants and marine sources are important elements of indigenous medical systems worldwide. The natural drugs from
medicinal plants and marine sources have received considerable interest in treatment of diabetes and inflammation. Based on
literature, alpha glucosidase, aldose reductase and PTP1B enzymes were chosen as anti-diabetes targets and PLA2 was chosen for
the anti-inflammatory target. In our study, plant and bromophenols (BPs) inhibitors were screened using High Throughput Virtual
screening (HTVS) followed by Induced Fit Docking (IFD) studies were carried out against diabetes and inflammation targets. The
IFD result of natural inhibitors has showed favorable docking score, glide energy and hydrogen bonds interactions with the active
site residues. Some of the natural inhibitors successively satisfied all the in silico parameters among the others and seem to be
potent inhibitors against diabetes and inflammation. 相似文献
156.
Exocellular Carbohydrase Formation by Rumen Holotrich Ciliates 总被引:1,自引:0,他引:1
A. G. WILLIAMS 《The Journal of eukaryotic microbiology》1979,26(4):665-672
SYNOPSIS Exocellular carbohydrase activity was detected, in the absence of cell lysis, in cell-free culture supernatant fluids of rumen holotrich ciliates after incubations in buffer systems of varying tonicity, from cell suspensions that were isolated by various technics, and in which bacterial activity had been suppressed by antibiotics. The kinetic characteristics of the holotrich invertases and β–glucosidase from Dasytricha , although having interspecies variations, were the same for the intra- and extracellular form of the enzyme. The properties of the invertase activity present in cell-free rumen contents resembled those of the exocellular enzymes formed by the holotrichs. Invertase activity in the in vitro culture supernatant fluid of Dasytricha ruminantium increased throughout the incubation period and was influenced by the initial pH, temperature, sucrose concentration, and inoculum size. Exocellular holotrich carbohydrase activity was increased when the incubation substrate was not readily utilized by the protozoa. Intracellular carbohydrase activity was also influenced by the carbohydrate substrate. 相似文献
157.
158.
Minzhuo Liu Xueqian Huang Qi Liu Xujie Li Miao Chen Yuqiu Zhu Xiaoqing Chen 《Phytochemical analysis : PCA》2019,30(6):661-668
159.
《Protein science : a publication of the Protein Society》2018,27(8):1498-1508
Carbohydrate hydrolyzing α‐glucosidases are commonly found in microorganisms present in the human intestine microbiome. We have previously reported crystal structures of an α‐glucosidase from the human gut bacterium Blaubia (Ruminococcus) obeum (Ro‐αG1) and its substrate preference/specificity switch. This novel member of the GH31 family is a structural homolog of human intestinal maltase‐glucoamylase (MGAM) and sucrase–isomaltase (SI) with a highly conserved active site that is predicted to be common in Ro‐αG1 homologs among other species that colonize the human gut. In this report, we present structures of Ro‐αG1 in complex with the antidiabetic α‐glucosidase inhibitors voglibose, miglitol, and acarbose and supporting binding data. The in vitro binding of these antidiabetic drugs to Ro‐αG1 suggests the potential for unintended in vivo crossreaction of the α‐glucosidase inhibitors to bacterial α‐glucosidases that are present in gut microorganism communities. Moreover, analysis of these drug‐bound enzyme structures could benefit further antidiabetic drug development. 相似文献
160.
William Parker Todd A. Wells Susanne Meza-Keuthen In-Soo Kim Pill-Soon Song 《Journal of Protein Chemistry》1995,14(2):53-57
Recently, Mummertet al. [Nature
363, 644–648 (1993)] isolated a proposed TCP1-related chaperone. Here we report several findings concerning the protein which they sequenced. Two similar N-terminal sequences were obtained from this abundant 60-kDa protein. Internal sequences were also acquired by protease digestion. Initially it was believed the protein was able to completely inhibit citrate synthase aggregation, but later purifications demonstrated that the 60-kDa polypeptide lacked both chaperone activity and the previously reported kinase activity [Grimmet al., Planta
178, 199–206 (1989)]. It is now our belief that this protein is neither a chaperone nor a kinase. 相似文献