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21.
Francisco M. Gírio Fátima Pelica M. T. Amaral-Collaço 《Applied biochemistry and biotechnology》1996,56(1):79-87
The xylitol dehydrogenase (EC 1.1.1.9) from xylose-grown cells ofDebaryomyces hansenii was partially purified in two Chromatographic steps, and characterization studies were carried out in order to inves tigate
the role of the xylitol dehydrogenase-catalyzed step in the regu lation of D-xylose metabolism. The enzyme was most active
at pH 9.0–9.5, and exhibited a broad polyol specificity. The Michaelis con stants for xylitol and NAD+ were 16.5 and 0.55 mM, respectively. Ca2+, Mg2+, and Mn2+ did not affect the enzyme activity. Conversely, Zn2+, Cd2+, and Co2+ strongly inhibited the enzyme activity. It was concluded that NAD+-xylitol dehydrogenase from D.hansenii has similarities with other xylose-fermenting yeasts in respect to optimal pH, substrate specificity, and Km value for xylitol, and therefore should be named L-iditol:NAD+-5-oxidoreductase (EC 1.1.1.14). The reason D.hansenii is a good xylitol producer is not because of its value of Km for xylitol, which is low enough to assure its fast oxidation by NAD+ xylitol dehydrogenase. However, a higher Km value of xylitol dehydro genase for NAD+ compared to theK
m
values of other xylose-ferment ing yeasts may be responsible for the higher xylitol yields. 相似文献
22.
Howell EE Shukla U Hicks SN Smiley RD Kuhn LA Zavodszky MI 《Journal of computer-aided molecular design》2001,15(11):1035-1052
R67 dihydrofolate reductase (DHFR) is a novel enzyme that confers resistance to the antibiotic trimethoprim. The crystal structure of R67 DHFR displays a toroidal structure with a central active-site pore. This homotetrameric protein exhibits 222 symmetry, with only a few residues from each chain contributing to the active site, so related sites must be used to bind both substrate (dihydrofolate) and cofactor (NADPH) in the productive R67 DHFR?NADPH?dihydrofolate complex. Whereas the site of folate binding has been partially resolved crystallographically, an interesting question remains: how can the highly symmetrical active site also bind and orient NADPH for catalysis? To model this ternary complex, we employed DOCK and SLIDE, two methods for docking flexible ligands into proteins using quite different algorithms. The bound pteridine ring of folate (Fol I) from the crystal structure of R67 DHFR was used as the basis for docking the nicotinamide-ribose-Pi (NMN) moiety of NADPH. NMN was positioned by both DOCK and SLIDE on the opposite side of the pore from Fol I, where it interacts with Fol I at the pore's center. Numerous residues serve dual roles in binding. For example, Gln 67 from both the B and D subunits has several contacts with the pteridine ring, while the same residue from the A and C subunits has several contacts with the nicotinamide ring. The residues involved in dual roles are generally amphipathic, allowing them to make both hydrophobic and hydrophilic contacts with the ligands. The result is a `hot spot' binding surface allowing the same residues to co-optimize the binding of two ligands, and orient them for catalysis. 相似文献
23.
An effective method was developed to use an enzyme in ionic liquids; the asymmetric reduction of ketones by Geotrichum candidum in ionic liquids proceeded smoothly with excellent enantioselectivity when the cell was immobilized on water-absorbing polymer containing water, while the reaction without the polymer did not proceed. 相似文献
24.
Ivanauskas F. Kaunietis I. Laurinavičius V. Razumienė J. Šimkus R. 《Journal of mathematical chemistry》2005,38(3):355-366
The plate-gap model of porous enzyme doped electrode has been proposed and analyzed. It was suggested that reaction diffusion conditions in pores of bulk electrode resemble particular conditions in thin gap between parallel conducting plates. The model is based on the diffusion equations containing a nonlinear term related to the Michaelis–Menten kinetic of the enzymatic reaction inside gap. Steady state current was calculated for the wide range of given parameters and substrate concentrations. All dependences of current on substrate concentration were approximated by hyperbolas in order to obtain “apparent” parameters (maximal currents and apparent Michaelis constants) of modelled biosensors. Simple approximate relationships between given and apparent parameters were derived. The applicability of theoretical plate-gap model was tested for the case of carbon paste electrodes which were doped with PQQ – dependent glucose dehydrogenase. It was found, that soluble glucose dehydrogenase based biosensors exhibit characteristic features of the theoretical plate-gap biosensors. 相似文献
25.
Arelí Durón-Castellanos Vanesa Zazueta-Novoa Hortencia Silva-Jiménez Yolanda Alvarado-Caudillo Eduardo Peña Cabrera Roberto Zazueta-Sandoval 《Applied biochemistry and biotechnology》2005,121(1-3):279-288
Different soluble NAD+-dependent alcohol dehydrogenase (ADH) isozymes were detected in cell-free homogenates from aerobically grown mycelia of YR-1
strain of Mucor circinelloides isolated from petroleumcontaminated soil samples. Depending on the carbon source present in the growth media, multiple NAD+-dependent ADHs were detected when hexadecane or decane was used as the sole carbon source in the culture media. ADH activities
from aerobically or anaerobically grown mycelium or yeast cells, respectively, were detected when growth medium with glucose
added was the sole carbon source; the enzyme activity exhibited optimum pH for the oxidation of different alcohols (methanol,
ethanol, and hexadecanol) similar to that of the corresponding aldehyde (≈7.0). Zymogram analysis conducted with partially
purified fractions of extracts from aerobic mycelium or anaerobic yeast cells of the YR-1 strain grown in glucose as the sole
carbon source indicated the presence of a single NAD+-dependent ADH enzyme in each case, and the activity level was higher in the yeast cells. ADH enzyme from mycelium grown in
different carbon sources showed high activity using ethanol as substrate, although higher activity was displayed when the
cells were grown in hexadecane as the sole carbon source. Zymogram analysis with these extracts showed that this particular
strain of M. circinelloides has four different isozymes with ADH activity and, interestingly, one of them, ADH4, was identified also as phenanthrene-diol-dehydrogenase,
an enzyme that possibly participates in the aromatic hydrocarbon biodegradation pathway. 相似文献
26.
《Arabian Journal of Chemistry》2022,15(12):104330
The present study was carried out to design and synthesize a number of novel aromatic carboxamide derivatives of dehydroabietylamine. The preliminary antifungal assay indicated that most of title compounds displayed moderate to good antifungal activity toward the six fungal strains in vitro. Compounds 3i, 3q, 4b and 4d showed significant antifungal activity against Sclerotinia sclerotiorum, with EC50 values ranging from 0.067 ~ 0.393 mg/L. Compounds 3i, 4b and 4d also showed pronounced mycelial growth inhibition activities against B. cinerea and A. solani. Furthermore, in the in vivo assay, compound 4b exhibited brilliant protective activity against S. sclerotiorum-infected rape leaves. Meanwhile, the in vivo bioassay on tomato plants infected by B. cinerea showed that compound 3i and 4d displayed excellent protective activity at 200 mg/L, which were near to boscalid. Primary mechanistic study revealed that 4b could inhibit sclerotia formation as well as reduce the exopolysaccharide level. SEM and TEM analysis indicated that 4b possessed a strong ability to destroy the surface morphology of mycelia, cell structure and seriously interfere with the growth of the fungal pathogen. In addition, 4b exhibited good inhibitory activity (IC50 = 23.3 ± 1.6 μM) toward succinate dehydrogenase (SDH). Molecular modeling study confirmed the binding modes between compound 4b and SDH. The above antifungal results and fungicidal mechanism study revealed that this class of dehydroabietylamine derivatives could be potential SDH inhibitors and lead compounds for novel fungicides development. 相似文献
27.
《Acta Crystallographica. Section C, Structural Chemistry》2017,73(7):546-555
A novel and potentially active dihydroorotate dehydrogenase (DHODH) inhibitor, namely 3‐({(E )‐[(E )‐1‐(biphenyl‐4‐yl)ethylidene]hydrazinylidene}methyl)‐1H‐indole (BEHI) acetonitrile disolvate, C23H19N3·2CH3CN, has been designed and synthesized. The structure of BEHI was characterized by elemental analysis, Q‐TOF (quadrupole time‐of‐flight) MS, NMR, UV–Vis and single‐crystal X‐ray diffraction. The antitumour activity of the target molecule was evaluated by the MTT method. Results indicated that BEHI exhibited rather potent cytotoxic activity against human A549 (IC50 = 20.5 µM ) and mouse breast 4T1 (IC50 = 18.5 µM ) cancer cell lines. Meanwhile, to rationalize its potencies in the target, BEHI was docked into DHODH and the interactions with the active site residues were analyzed. Single‐crystal structure analysis indicated that hydrogen bonds are present only between BEHI and acetonitrile solvent molecules in the asymmetric unit. The interplay of weak π–π stacking and weak C(N)—H…π interactions between neighbouring BEHI molecules play crucial roles in the formation of the final supramolecular frameworks. 相似文献
28.
Determination of the inhibitory effect of green tea extract on glucose‐6‐phosphate dehydrogenase based on multilayer capillary enzyme microreactor 下载免费PDF全文
Mohamed Amara Camara Miaomiao Tian Xiaoxia Liu Xin Liu Yujia Wang Jiqing Yang Li Yang 《Biomedical chromatography : BMC》2016,30(8):1210-1215
Natural herbal medicines are an important source of enzyme inhibitors for the discovery of new drugs. A number of natural extracts such as green tea have been used in prevention and treatment of diseases due to their low‐cost, low toxicity and good performance. The present study reports an online assay of the activity and inhibition of the green tea extract of the Glucose 6‐phosphate dehydrogenase (G6PDH) enzyme using multilayer capillary electrophoresis based immobilized enzyme microreactors (CE‐IMERs). The multilayer CE‐IMERs were produced with layer‐by‐layer electrostatic assembly, which can easily enhance the enzyme loading capacity of the microreactor. The activity of the G6PDH enzyme was determined and the enzyme inhibition by the inhibitors from green tea extract was investigated using online assay of the multilayer CE‐IMERs. The Michaelis constant (Km) of the enzyme, the IC50 and Ki values of the inhibitors were achieved and found to agree with those obtained using offline assays. The results show a competitive inhibition of green tea extract on the G6PDH enzyme. The present study provides an efficient and easy‐to‐operate approach for determining G6PDH enzyme reaction and the inhibition of green tea extract, which may be beneficial in research and the development of natural herbal medicines. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
29.
Following our efforts towards the synthesis of new potential inhibitors of Xanthine Dehydrogenase (XDH), we describe here a general method for the preparation of N-(5-oxo-2,5-dihydro)pyrrol-3-yl glycines and N-(5-oxo-2,5-dihydro)pyrrol-3-yl glycine esters from glycine ethyl ester hydrochloride and various 4-hydroxy-5-oxo-2,5-dihydro-1H-pyrrole-3-carboxylic acid esters and carbonitriles. 相似文献
30.
Daria Kupczyk Renata Studziska Szymon Baumgart Rafa Bilski Tomasz Kosmalski Renata Koodziejska Alina Wo
niak 《Molecules (Basel, Switzerland)》2021,26(9)
Tumors are currently more and more common all over the world; hence, attempts are being made to explain the biochemical processes underlying their development. The search for new therapeutic pathways, with particular emphasis on enzymatic activity and its modulation regulating the level of glucocorticosteroids, may contribute to the development and implementation of new therapeutic options in the treatment process. Our research focuses on understanding the role of 11β-HSD1 and 11β-HSD2 as factors involved in the differentiation and proliferation of neoplastic cells. In this work, we obtained the 9 novel N-tert-butyl substituted 2-aminothiazol-4(5H)-one (pseudothiohydantoin) derivatives, differing in the substituents at C-5 of the thiazole ring. The inhibitory activity and selectivity of the obtained derivatives in relation to two isoforms of 11β-HSD were evaluated. The highest inhibitory activity for 11β-HSD1 showed compound 3h, containing the cyclohexane substituent at the 5-position of the thiazole ring in the spiro system (82.5% at a conc. 10 µM). On the other hand, the derivative 3f with the phenyl substituent at C-5 showed the highest inhibition of 11β-HSD2 (53.57% at a conc. of 10 µM). A low selectivity in the inhibition of 11β-HSD2 was observed but, unlike 18β-glycyrrhetinic acid, these compounds were found to inhibit the activity of 11β-HSD2 to a greater extent than 11β-HSD1, which makes them attractive for further research on their anti-cancer activity. 相似文献