共查询到20条相似文献,搜索用时 31 毫秒
1.
Simona Maria Monti Giuseppina De Simone Nina A. Dathan Martha Ludwig Daniela Vullo Andrea Scozzafava Clemente Capasso Claudiu T. Supuran 《Bioorganic & medicinal chemistry letters》2013,23(6):1626-1630
Several β-carbonic anhydrases (CAs, EC 4.2.1.1) are present in all land plants examined thus far. Here we report the first detailed biochemical characterization of one such isoform, FbiCA 1, from the C4 plant Flaveria bidentis, which was cloned, purified and characterized as recombinant protein. FbiCA 1 has an interesting CO2 hydrase catalytic activity (kcat of 1.2 × 105 and kcat/Km of 7.5 × 106 M?1 × s?1) and was moderately inhibited by most simple/complex inorganic anions. Potent FbiCA 1 inhibitors were also detected, such as trithiocarbonate, diethyldithiocarbamate, sulfamide, sulfamic acid, phenylboronic acid and phenylarsonic acid (KIs in the range of 4–60 μM). Such inhibitors may be used as tools to better understand the role of various β-CA isoforms in photosynthesis. 相似文献
2.
K.S. Shashidhara Sushama M. Gaikwad 《International journal of biological macromolecules》2009,44(1):112-115
Energetics of the catalysis of Class II α-mannosidase (E.C.3.2.1.24) from Aspergillus fischeri was studied. The enzyme showed Kcat/Km for Man (α1-3) Man, Man (α1-2) Man and Man (α1-6) Man as 7488, 5376 and 3690 M?1 min?1, respectively. The activation energy, Ea was 15.14, 47.43 and 71.21 kJ/mol for α1-3, α1-2 and α1-6 linked mannobioses, respectively, reflecting the energy barrier in the hydrolysis of latter two substrates. The enzyme showed Kcat/Km as 3.56 × 105 and 4.61 × 105 M?1 min?1 and Ea as 38.7 and 8.92 kJ/mol, towards pNPαMan and 4-MeUmbαMan, respectively. Binding of Swainsonine to the enzyme is stronger than that of 1-deoxymannojirimycin. 相似文献
3.
Lilu Guo Alirica I. Suarez Michael R. Braden John M. Gerdes Charles M. Thompson 《Bioorganic & medicinal chemistry letters》2010,20(3):1194-1197
Fluorophosphonate (FP) head groups were tethered to a variety of chromophores (C) via a triazole group and tested as FPC inhibitors of recombinant mouse (rMoAChE) and electric eel (EEAChE) acetylcholinesterase. The inhibitors showed bimolecular inhibition constants (ki) ranging from 0.3 × 105 M?1 min?1 to 10.4 × 105 M?1 min?1. When tested against rMoAChE, the dansyl FPC was 12.5-fold more potent than the corresponding inhibitor bearing a Texas Red as chromophore, whereas the Lissamine and dabsyl chromophores led to better anti-EEAChE inhibitors. Most inhibitors were equal or better inhibitors of rMoAChE than EEAChE. 3-Azidopropyl fluorophosphonate, which served as one of the FP head groups, showed excellent inhibitory potency against both AChE’s (? 1 × 107 M?1 min?1) indicating, in general, that addition of the chromophore reduced the overall anti-AChE activity. Covalent attachment of the dabsyl-FPC analog to rMoAChE was demonstrated using size exclusion chromatography and spectroscopic analysis, and visualized using molecular modeling. 相似文献
4.
Sameer Chavda Balaji Babu Pravin Patil Adam Plaunt Amanda Ferguson Megan Lee Samuel Tzou Robert Sjoholm Toni Rice Hilary Mackay Joseph Ramos Shuo Wang Shicai Lin Konstantinos Kiakos W. David Wilson John A. Hartley Moses Lee 《Bioorganic & medicinal chemistry》2013,21(13):3907-3918
Orthogonally positioned diamino/dicationic polyamides (PAs) have good water solubility and enhanced binding affinity, whilst retaining DNA minor groove and sequence specificity compared to their monoamino/monocationic counterparts. The synthesis and DNA binding properties of the following diamino PAs: f-IPI (3a), f-IPP (4), f-PIP (5), and f-PPP (6) are described. P denotes the site where a 1-propylamino group is attached to the N1-position of the heterocycle. Binding of the diamino PAs to DNA was assessed by DNase I footprinting, thermal denaturation, circular dichroism titration, biosensor surface plasmon resonance (SPR), and isothermal titration calorimetry (ITC) studies. According to SPR studies, f-IPI (3a) bound more strongly (Keq = 2.4 × 108 M?1) and with comparable sequence selectivity to its cognate sequence 5′-ACGCGT-3′ when compared to its monoamino analog f-IPI (1). The binding of f-IPI (3a) to 5′-ACGCGT-3′ via the stacked dimer motif was balanced between enthalpy and entropy, and that was quite different from the enthalpy-driven binding of its monoamino parent f-IPI (1). f-IPP (4) also bound more strongly to its cognate sequence 5′-ATGCAT-3′ (Keq = 7.4 × 106 M?1) via the side-by-side stacked motif than its monoamino analog f-IPP (2a). Although f-PPP (6) bound via a 1:1 motif, it bound strongly to its cognate sequence 5′-AAATTT-3′ (Keq = 4.8 × 107 M?1), 15-times higher than the binding of its monoamino analog f-PPP (2c), albeit f-PPP bound via the stacked motif. Finally, f-PIP (5) bound to its target sequence 5′-ATCGAT-3′ as a stacked dimer and it has the lowest affinity among the diamino PAs tested (Keq <1 × 105 M?1). This was about two times lower in affinity than the binding of its monoamino analog f-PIP (2b). The results further demonstrated that the ‘core rules’ of DNA recognition by monoamino PAs also apply to their diamino analogs. Specifically, PAs that contain a stacked IP core structure bind most strongly (highest binding constants) to their cognate GC doublet, followed by the binding of PAs with a stacked PP structure to two degenerate AT base pairs, and finally the binding of PAs with a PI core to their cognate CG doublet. 相似文献
5.
Saibal Chakraborty Niti H. Shah James C. Fishbein Ramachandra S. Hosmane 《Bioorganic & medicinal chemistry letters》2012,22(23):7214-7218
In our long and broad program to explore structure–activity relationships of the natural product azepinomycin and its analogues for inhibition of guanase, an important enzyme of purine salvage pathway of nucleic acid metabolism, it became necessary to investigate if the nucleoside analogues of the heterocycle azepinomycin, which are likely to be formed in vivo, would be more or less potent than the parent heterocycle. To this end, we have resynthesized both azepinomycin (1) and its two diastereomeric nucleoside analogues (2 and 3), employing a modified, more efficient procedure, and have biochemically screened all three compounds against a mammalian guanase. Our results indicate that the natural product is at least 200 times more potent toward inhibition of guanase as compared with its nucleoside analogues, with the observed Ki of azepinomycin (1) against the rabbit liver guanase = 2.5 (±0.6) × 10?6 M, while Ki of Compound 2 = 1.19 (±0.02) × 10?4 M and that of Compound 3 = 1.29 (±0.03) × 10?4 M. It is also to be noted that while IC50 value of azepinomycin against guanase in cell culture has long been reported, no inhibition studies nor Ki against a pure mammalian enzyme have ever been documented. In addition, we have, for the first time, determined the absolute stereochemistry of the 6-OH group of 2 and 3 using conformational analysis coupled with 2-D 1H NMR NOESY 相似文献
6.
Semra Isik Feray Kockar Meltem Aydin Oktay Arslan Ozen Ozensoy Guler Alessio Innocenti Andrea Scozzafava Claudiu T. Supuran 《Bioorganic & medicinal chemistry》2009,17(3):1158-1163
The protein encoded by the Nce103 gene of Saccharomyces cerevisiae, a β-carbonic anhydrase (CA, EC 4.2.1.1) designated as scCA, has been cloned, purified, characterized kinetically and investigated for its inhibition with a series of sulfonamides and one sulfamate. The enzyme showed high CO2 hydrase activity, with a kcat of 9.4 × 105 s?1, and kcat/KM of 9.8 × 107 M?1 s?1. Simple benzenesulfonamides substituted in 2-, 4- and 3,4-positions of the benzene ring with amino, alkyl, halogeno and hydroxyalkyl moieties were weak scCA inhibitors with KIs in the range of 0.976–18.45 μM. Better inhibition (KIs in the range of 154–654 nM) was observed for benzenesulfonamides incorporating aminoalkyl/carboxyalkyl moieties or halogenosulfanilamides; benzene-1,3-disulfonamides; simple heterocyclic sulfonamides and sulfanilyl-sulfonamides. The clinically used sulfonamides/sulfamate (acetazolamide, ethoxzolamide, methazolamide, dorzolamide, topiramate, celecoxib, etc.) generally showed effective scCA inhibitory activity, with KIs in the range of 82.6–133 nM. The best inhibitor (KI of 15.1 nM) was 4-(2-amino-pyrimidin-4-yl)-benzenesulfonamide. These inhibitors may be useful to better understand the physiological role of β-CAs in yeast and some pathogenic fungi which encode orthologues of the yeast enzyme and eventually for designing novel antifungal therapies. 相似文献
7.
Sony Soman Michelle J. Yoo Yoon Jeong Jang David S. Hage 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2010,878(7-8):705-708
High-performance affinity chromatography was used to study binding by the drug lidocaine to human serum albumin (HSA) and α1-acid glycoprotein (AGP). AGP had strong binding to lidocaine, with an association equilibrium constant (Ka) of 1.1–1.7 × 105 M?1 at 37 °C and pH 7.4. Lidocaine had weak to moderate binding to HSA, with a Ka in the range of 103 to 104 M?1. Competitive experiments with site selective probes showed that lidocaine was interacting with Sudlow site II of HSA and the propranolol site of AGP. These results agree with previous observations in the literature and provide a better quantitative understanding of how lidocaine binds to these serum proteins and is transported in the circulation. This study also demonstrates how HPAC can be used to examine the binding of a drug with multiple serum proteins and provide detailed information on the interaction sites and equilibrium constants that are involved in such processes. 相似文献
8.
《Bioorganic & medicinal chemistry》2016,24(4):835-840
We have cloned, purified and characterized the γ-carbonic anhydrase (CA, EC 4.2.1.1) present in the genome of the Antarctic bacterium Colwellia psychrerythraea, which is an obligate psychrophile. The enzyme shows a significant catalytic activity for the physiologic reaction of CO2 hydration to bicarbonate and protons, with the following kinetic parameters: kcat of 6.0 × 105 s−1 and a kcat/Km of 4.7 × 106 M−1 × s−1. This activity was inhibited by the sulfonamide CA inhibitor (CAI) acetazolamide, with a KI of 502 nM. A range of anions was also investigated for their inhibitory action against the new enzyme CpsCA. Perchlorate, tetrafluoroborate, fluoride and bromide were not inhibitory, whereas cyanate, thiocyanate, cyanide, hydrogensulfide, carbonate and bicarbonate showed KIs in the range of 1.4–4.4 mM. Diethyldithiocarbamate was a better inhibitor (KI of 0.58 mM) whereas sulfamide, sulfamate, phenylboronic acid and phenylarsonic acid were the most effective inhibitors detected, with KIs ranging between 8 and 38 μM. The present study may shed some more light regarding the role that γ-CAs play in the life cycle of psychrophilic bacteria as the Antarctic one investigated here. 相似文献
9.
Daniela Vullo Isao Nishimori Andrea Scozzafava Stephan Köhler Jean-Yves Winum Claudiu T. Supuran 《Bioorganic & medicinal chemistry letters》2010,20(7):2178-2182
A β-carbonic anhydrase (CA, EC 4.2.1.1) from the bacterial pathogen Brucella suis, bsCA 1, has been cloned, purified characterized kinetically and for inhibition with a series of water soluble glycosylated sulfanilamides. bsCA 1 has appreciable activity as catalyst for the hydration of CO2 to bicarbonate, with a kcat of 6.4 × 105 s?1 and kcat/Km of 3.9 × 107 M?1 s?1. All types of inhibitory activities have been detected, with KIs in the range of 8.9–110 nM. The best bsCA 1 inhibitor were the galactose and ribose sulfanilamides, with inhibition constants of 8.9–9.2 nM. Small structural changes in the sugar moiety led to dramatic differences of enzyme inhibitory activity for this series of compounds. One of the tested glycosylsulfonamides and acetazolamide significantly inhibited the growth of the bacteria in cell cultures. 相似文献
10.
Zahra Mojallal-Tabatabei Ahmad Asoodeh Mohammad Reza Housaindokht Jamshidkhan Chamani 《Process Biochemistry》2013,48(7):1091-1098
This work reports the purification and biochemical characterization of angiotensin I-converting enzyme (ACE) from ostrich (Struthio camelus) lung. The molecular weight of the purified enzyme was approximately evaluated to be 200 kDa and the maximum enzyme activity was observed at pH 7.5. The enzyme activity was increased by detergents of Triton X-100 (0.01%), cetyltrimethylammonium bromide (CTAB) (0.1 and 1 mM) and sodium dodecyl sulfate (SDS) (0.1 mM), while decreased by Triton X-100 (1% and 10%) and SDS (1 mM and 10 mM). The secondary and tertiary structure and activity of ACE in the absence and presence of trifluoroethanol (TFE) were investigated using circular dichroism, fluorescence quenching and UV–visible spectroscopy, respectively. Our results revealed that TFE stabilizes ACE at low concentrations, while acts as a denaturant at higher concentration (20%). The Km, Kcat and Kcat/Km values of ostrich ACE towards FAPGG were 0.8 × 10?4 M, 59,240 min?1 and 74 × 107 min?1 M?1, respectively. The values of IC50 and Ki for captopril were determined to be 36.5 nM and 16.6 nM, respectively. In conclusion, ostrich lung ACE is a new enzyme which could be employed as a candidate for studying ACE structure and its natural or synthetic inhibitors. 相似文献
11.
《Bioorganic & medicinal chemistry letters》2014,24(4):1127-1132
We investigated the cloning, catalytic activity and anion inhibition of the β-class carbonic anhydrases (CAs, EC 4.2.1.1) from the bacterial pathogen Legionella pneumophila. Two such enzymes, lpCA1 and lpCA2, were found in the genome of this pathogen. These enzymes were determined to be efficient catalysts for CO2 hydration, with kcat values in the range of (3.4–8.3) × 105 s−1 and kcat/KM values of (4.7–8.5) × 107 M−1 s−1. A set of inorganic anions and small molecules was investigated to identify inhibitors of these enzymes. Perchlorate and tetrafluoroborate were not acting as inhibitors (KI >200 mM), whereas sulfate was a very weak inhibitor for both lpCA1 and lpCA2 (KI values of 77.9–96.5 mM). The most potent lpCA1 inhibitors were cyanide, azide, hydrogen sulfide, diethyldithiocarbamate, sulfamate, sulfamide, phenylboronic acid and phenylarsonic acid, with KI values ranging from 6 to 94 μM. The most potent lpCA2 inhibitors were diethyldithiocarbamate, sulfamide, sulfamate, phenylboronic acid and phenylarsonic acid, with KI values ranging from 2 to 13 μM. As these enzymes seem to be involved in regulation of phagosome pH during Legionella infection, inhibition of these targets may lead to antibacterial agents with a novel mechanism of action. 相似文献
12.
《Bioorganic & medicinal chemistry》2016,24(18):4410-4414
We have cloned, purified and investigated the catalytic activity and anion inhibition profiles of a full catalytic domain (358 amino acid residues) carbonic anhydrase (CA, EC 4.2.1.1) from Plasmodium falciparum, PfCAdom, an enzyme belonging to the η-CA class and identified in the genome of the malaria-producing protozoa. A truncated such enzyme, PfCA1, containing 235 residues was investigated earlier for its catalytic and inhibition profiles. The two enzymes were efficient catalysts for CO2 hydration: PfCAdom showed a kcat of 3.8 × 105 s−1 and kcat/Km of 7.2 × 107 M−1 × s−1, whereas PfCA showed a lower activity compared to PfCAdom, with a kcat of 1.4 × 105 s−1 and kcat/Km of 5.4 × 106 M−1 × s−1. PfCAdom was generally less inhibited by most anions and small molecules compared to PfCA1. The best PfCAdom inhibitors were sulfamide, sulfamic acid, phenylboronic acid and phenylarsonic acid, which showed KIs in the range of 9–68 μM, followed by bicarbonate, hydrogensulfide, stannate and N,N-diethyldithiocarbamate, which were submillimolar inhibitors, with KIs in the range of 0.53–0.97 mM. Malaria parasites CA inhibition was proposed as a new strategy to develop antimalarial drugs, with a novel mechanism of action. 相似文献
13.
Fabrizio Carta Alfonso Maresca Adrian Suarez Covarrubias Sherry L. Mowbray T. Alwyn Jones Claudiu T. Supuran 《Bioorganic & medicinal chemistry letters》2009,19(23):6649-6654
The Rv3588c gene product of Mycobacterium tuberculosis, a β-carbonic anhydrase (CA, EC 4.2.1.1) denominated here mtCA 2, shows the highest catalytic activity for CO2 hydration (kcat of 9.8 × 105 s?1, and kcat/Km of 9.3 × 107 M?1 s?1) among the three β-CAs encoded in the genome of this pathogen. A series of sulfonamides/sulfamates was assayed for their interaction with mtCA 2, and some diazenylbenzenesulfonamides were synthesized from sulfanilamide/metanilamide by diazotization followed by coupling with amines or phenols. Several low nanomolar mtCA 2 inhibitors have been detected among which acetazolamide, ethoxzolamide and some 4-diazenylbenzenesulfonamides (KIs of 9–59 nM). As the Rv3588c gene was shown to be essential to the growth of M. tuberculosis, inhibition of this enzyme may be relevant for the design of antituberculosis drugs possessing a novel mechanism of action. 相似文献
14.
Ensifer (Sinorhizobium) meliloti is a nitrogen-fixing α-proteobacterium able to biosynthesize the osmoprotectant glycine betaine from choline sulfate through a metabolic pathway that starts with the enzyme choline-O-sulfatase. This protein seems to be widely distributed in microorganisms and thought to play an important role in their sulfur metabolism. However, only crude extracts with choline sulfatase activity have been studied. In this work, Ensifer (Sinorhizobium) meliloti choline-O-sulfatase was obtained in a high degree of purity after expression in Escherichia coli. Gel filtration and dynamic light scattering experiments showed that the recombinant enzyme exists as a dimer in solution. Using calorimetry, its catalytic activity against its natural substrate, choline-O-sulfate, gave a kcat=2.7×10?1 s?1 and a KM=11.1 mM. For the synthetic substrates p-nitrophenyl sulfate and methylumbelliferyl sulfate, the kcat values were 3.5×10?2 s?1 and 4.3×10?2 s?1, with KM values of 75.8 and 11.8 mM respectively. The low catalytic activity of the recombinant sulfatase was due to the absence of the formylglycine post-translational modification in its active-site cysteine 54. Nevertheless, unmodified Ensifer (Sinorhizobium) meliloti choline-O-sulfatase is a multiple-turnover enzyme with remarkable catalytic efficiency. 相似文献
15.
16.
Partha Pratim Bose Surajit Bhattacharjee Shuvendu Singha Santanu Mandal Gautam Mondal Priya Gupta Bishnu P. Chatterjee 《Biochemistry and Biophysics Reports》2016
BackgroundLectins are highly important biomolecules to study several biological processes. A novel α-D-glucose/mannose specific lectin was isolated from the seeds of litchi fruits (Litchi chinensis) and its various biophysical and biochemical properties were studied.MethodsPurification was done by successive Sephadex G 100 and Con A-Sepharose 4B affinity chromatography. SDS-PAGE, Surface Plasmon Resonance (SPR), steady state absorbance, fluorescence, time-correlated single-photon counting, circular dichroism and antibiofilm activity by measuring total protein estimation and azocasein degradation assay have been performed.ResultsThe purified lectin is a homodimer of molecular mass ~ 54 kDa. The amount of lectin required for hemagglutination of normal human O erythrocytes was 6.72 µg/ml. Among the saccharides tested, Man-α-(1,6)-Man was found to be the most potent inhibitor (0.01 mM) determined by hemagglutination inhibition assay. Steady state and time resolved fluorescence measurements revealed that litchi lectin formed ground state complex with maltose (Ka=4.9 (±0.2)×104 M?1), which indicated static quenching (Stern-Volmer (SV) constant Ksv=4.6 (±0.2)×104 M?1). CD measurements demonstrated that litchi lectin showed no overall conformational change during the binding process with maltose. The lectin showed antibiofilm activity against Pseudomonus aeruginosa.ConclusionsA novel homodimeric lectin has been purified from the seeds of litchi fruits (Litchi chinensis) having specificity for α-d-glucose/mannose. The thermodynamics and conformational aspects of its interaction with maltose have been studied in detail. The antibiofilm activity of this lectin towards Pseudomonus aeruginosa has been explored.General significanceThe newly identified litchi lectin is highly specific for α-d-glucose/mannose with an important antibiofilm activity towards Pseudomonus aeruginosa. 相似文献
17.
Alessio Innocenti Worraanong Leewattanapasuk Fritz A. Mühlschlegel Antonio Mastrolorenzo Claudiu T. Supuran 《Bioorganic & medicinal chemistry letters》2009,19(16):4802-4805
A β-carbonic anhydrase (CA, EC 4.2.1.1), the protein encoded by the NCE103 gene of Candida glabrata which also present in Candida albicans and Saccharomyces cerevisiae, was cloned, purified, characterized kinetically and investigated for its inhibition by a series simple, inorganic anions such as halogenides, pseudohalogenides, bicarbonate, carbonate, nitrate, nitrite, hydrogen sulfide, bisulfite, perchlorate, sulfate and some isosteric species. The enzyme showed significant CO2 hydrase activity, with a kcat of 3.8 × 105 s?1 and kcat/KM of 4.8 × 107 M?1 s?1. The Cà glabrata CA (CgCA) was moderately inhibited by metal poisons (cyanide, azide, cyanate, thiocyanate, KIs of 0.60–1.12 mM) but strongly inhibited by bicarbonate, nitrate, nitrite and phenylarsonic acid (KIs of 86–98 μM). The other anions investigated showed inhibition constants in the low millimolar range, with the exception of bromide and iodide (KIs of 27–42 mM). 相似文献
18.
《Bioorganic & medicinal chemistry》2014,22(11):2939-2946
Two β-carbonic anhydrases (CAs, EC 4.2.1.1) were identified, cloned and purified in the pathogenic bacterium Legionella pneumophila, denominated LpCA1 and LpCA2. They efficiently catalyze CO2 hydration to bicarbonate and protons, with kcat in the range of (3.4–8.3) × 105 s−1 and kcat/Km of (4.7–8.5) × 107 M−1 s−1, and are inhibited by sulfonamides and sulfamates. The best LpCA1 inhibitors were aminobenzolamide and structurally similar sulfonylated aromatic sulfonamides, as well as acetazolamide and ethoxzolamide(KIs in the range of 40.3–90.5 nM). The best LpCA2 inhibitors belonged to the same class of sulfonylated sulfonamides, together with acetazolamide, methazolamide and dichlorophenamide (KIs in the range of 25.2–88.5 nM). As these enzymes may be involved in pH regulation in the phagosome during Legionella infection, their inhibition may lead to antibacterials with a novel mechanism of action. 相似文献
19.
Altaf Hussain Muhammad Hamid Rashid Raheela Perveen Muhammad Ashraf 《Plant Physiology and Biochemistry》2009,47(3):188-194
We report for the first time kinetic and thermodynamic properties of soluble acid invertase (SAI) of sugarcane (Saccharum officinarum L.) salt sensitive local cultivar CP 77-400 (CP-77). The SAI was purified to apparent homogeneity on FPLC system. The crude enzyme was about 13 fold purified and recovery of SAI was 35%. The invertase was monomeric in nature and its native molecular mass on gel filtration and subunit mass on SDS-PAGE was 28 kDa. SAI was highly acidic having an optimum pH lower than 2. The acidic limb was missing. Proton transfer (donation and receiving) during catalysis was controlled by the basic limb having a pKa of 2.4. Carboxyl groups were involved in proton transfer during catalysis. The kinetic constants for sucrose hydrolysis by SAI were determined to be: km = 55 mg ml?1, kcat = 21 s?1, kcat/km = 0.38, while the thermodynamic parameters were: ΔH* = 52.6 kJ mol?1, ΔG* = 71.2 kJ mol?1, ΔS* = ?57 J mol?1 K?1, ΔG*E–S = 10.8 kJ mol?1 and ΔG*E–T = 2.6 kJ mol?1. The kinetics and thermodynamics of irreversible thermal denaturation at various temperatures 53–63 °C were also determined. The half -life of SAI at 53 and 63 °C was 112 and 10 min, respectively. At 55 °C, surprisingly the half -life increased to twice that at 53 °C. ΔG*, ΔH* and ΔS* of irreversible thermal stability of SAI at 55 °C were 107.7 kJ mol?1, 276.04 kJ mol?1 and 513 J mol?1K?1, respectively. 相似文献
20.
Alessio Innocenti Claudiu T. Supuran 《Bioorganic & medicinal chemistry letters》2010,20(21):6208-6212
Carbonic anhydrases (CAs, EC 4.2.1.1) belonging to α-, β-, γ- and ζ-classes and from various organisms, ranging from the bacteria, archaea to eukarya domains, were investigated for their esterase/phosphatase activity with 4-nitrophenyl acetate, 4-nitrophenyl phosphate and paraoxon as substrates. Only α-CAs showed esterase/phosphatase activity, whereas enzymes belonging to the β-, γ- and ζ-classes were completely devoid of such activity. Paraoxon, the metabolite of the organophosphorus insecticide parathione, was a much better substrate for several human/murine α-CA isoforms (CA I, II and XIII), with kcat/KM in the range of 2681.6–4474.9 M?1 s?1, compared to 4-nitrophenyl phosphate (kcat/KM of 14.9–1374.4 M?1 s?1). 相似文献