Cupric ion catalyzed ester hydrolysis of O-acetyl-2-pyridinecarboxaldoxime. Nucleophilic attack by metal-bound water

1982 ◽  
Vol 104 (6) ◽  
pp. 1654-1657 ◽  
Author(s):  
Junghun Suh ◽  
Minsek Cheong ◽  
Myunghyun Paik Suh
Keyword(s):  
Bound Water ◽  
Ester Hydrolysis ◽  
Nucleophilic Attack ◽  
Cupric Ion ◽  
Hydrolysis Of

Role of trinuclear Zn(II) complexes in promoting the hydrolysis of 4-nitrophenyl acetate

2004 ◽  
Vol 82 (3) ◽  
pp. 409-417 ◽  
Author(s):  
Qing-Chun Ge ◽  
Yan-He Guo ◽  
Hai Lin ◽  
Dong-Zhao Gao ◽  
Hua-Kuan Lin ◽  
...  
Keyword(s):  
Rate Constants ◽  
Volume Fraction ◽  
Bound Water ◽  
Catalytic Efficiency ◽  
Active Species ◽  
Nucleophilic Attack ◽  
Carboxyl Oxygen Atom ◽  
Ph Range ◽  
Hydrolysis Of

Potentiometric determination shows that trinuclear Zn(II) complexes of the four tripods 1,3,5-tri(2′,5′-diazahexyl)benzene (L1), 1,3,5-tri(2′,5′-diazaheptyl)benzene (L2), 1,3,5-tri(2′,5′-diazaoctyl)benzene (L3), and 1,3,5-tri(2′,5′-diazanonyl)benzene (L4) could be potential hydrolytic catalysts. CH3CN solutions containing [3Zn:L]T (0.5~2 × 10–3 mol·dm–3) with I = 0.10 mol·dm–3 of KNO3 and Good's buffer (10% volume fraction) were studied for the catalyzing hydrolysis of p-nitrophenyl acetate (NA, 0.5~2 × 10–3 mol·dm–3), at 298 K, in the 6.5–8.2 pH range. The observed rate constants, kobs, fit the equilibrium equation kobs = kcom [3Zn:L]T + kOH[OH–] + k0. The sigmoid pH~kcom profiles for NA hydrolysis suggest that either the Zn(II)-bound hydroxyl or the Zn(II)-bound water forms of the catalysts can be the active species. The observed second-order rate constants are 0.0082, 0.011, 0.0059, and 0.0019 mol–1·dm3·s–1 for the four Zn3L–H2O complexes (kA) and 0.342, 0.257, 0.382, and 0.091 mol–1·dm3·s–1 for the four Zn3L–OH- groups (kB), respectively. However, under the condition that [NA] = 0.5 × 10–3 mol·dm–3 and [3Zn:L1]T = 2~4 × 10–2 mol·dm–3 at pH 7.6, the observed rate constants, kobs, obey the equilibrium kobs = kcom[3Zn:L]T/(1/K′ + [3Zn:L]T). This indicates that the 3:1 complex (or its deprotonated hydroxide form) mediates NA hydrolysis by nucleophilic attack of the carboxyl center with the pre-formation of a coordination bond between the carboxyl oxygen atom and the Zn(II) ion. Comparison with other models was made, and the reasons for the high catalytic efficiency of the tripodal complexes were given.Key words: tripod, Zn(II), catalysis, NA hydrolysis, polynuclear.

scholarly journals The Mechanisms of Catalysis by Metallo -Lactamases

2008 ◽  
Vol 2008 ◽  
pp. 1-14 ◽  
Author(s):  
Michael I. Page ◽  
Adriana Badarau
Keyword(s):  
Water Molecule ◽  
Metal Ion ◽  
Hydrolytic Enzymes ◽  
Bound Water ◽  
Intrinsic Property ◽  
Carbonyl Oxygen ◽  
Nucleophilic Attack ◽  
Metal Ion Binding ◽  
Lactam Carbonyl ◽  
Hydrolysis Of

Class B -lactamases or metallo--lactamases (MBLs) require zinc ions to catalyse the hydrolysis of -lactam antibiotics such as penicillins, cephalosporins, carbapenems, and cephamycins. There are no clinically useful inhibitors against MBLs which are responsible for the resistance of some bacteria to antibiotics. There are two metal-ion binding sites that have different zinc ligands but the exact roles of the metal-ion remain controversial, and distinguishing between their relative importance is complex. The metal-ion can act as a Lewis acid by co-ordination to the -lactam carbonyl oxygen to facilitate nucleophilic attack and stabilise the negative charge developed on this oxygen in the tetrahedral intermediate anion. The metal-ion also lowers the pKa of the directly co-ordinated water molecule so that the metal-bound hydroxide ion is a better nucleophile than water and is used to attack the -lactam carbonyl carbon. An intrinsic property of binuclear metallo hydrolytic enzymes that depend on a metal-bound water both as the attacking nucleophile and as a ligand for the second metal-ion is that this water molecule, which is consumed during hydrolysis of the substrate, has to be replaced to maintain the catalytic cycle. With MBL this is reflected in some unusual kinetic profiles.

scholarly journals Pseudomonas putida MPE, a manganese-dependent endonuclease of the binuclear metallophosphoesterase superfamily, incises single-strand DNA in two orientations to yield a mixture of 3′-PO4 and 3′-OH termini

2020 ◽  
Author(s):  
Shreya Ghosh ◽  
Anam Ejaz ◽  
Lucas Repeta ◽  
Stewart Shuman
Keyword(s):  
Pseudomonas Putida ◽  
Bound Water ◽  
Acid Catalyst ◽  
Nuclease Activity ◽  
Single Strand ◽  
Dna Endonuclease ◽  
Dependent Endonuclease ◽  
Leaving Group ◽  
Phosphodiester Hydrolysis ◽  
Hydrolysis Of

Abstract Pseudomonas putida MPE exemplifies a novel clade of manganese-dependent single-strand DNA endonuclease within the binuclear metallophosphoesterase superfamily. MPE is encoded within a widely conserved DNA repair operon. Via structure-guided mutagenesis, we identify His113 and His81 as essential for DNA nuclease activity, albeit inessential for hydrolysis of bis-p-nitrophenylphosphate. We propose that His113 contacts the scissile phosphodiester and serves as a general acid catalyst to expel the OH leaving group of the product strand. We find that MPE cleaves the 3′ and 5′ single-strands of tailed duplex DNAs and that MPE can sense and incise duplexes at sites of short mismatch bulges and opposite a nick. We show that MPE is an ambidextrous phosphodiesterase capable of hydrolyzing the ssDNA backbone in either orientation to generate a mixture of 3′-OH and 3′-PO4 cleavage products. The directionality of phosphodiester hydrolysis is dictated by the orientation of the water nucleophile vis-à-vis the OH leaving group, which must be near apical for the reaction to proceed. We propose that the MPE active site and metal-bound water nucleophile are invariant and the enzyme can bind the ssDNA productively in opposite orientations.

Reaktionsbeteiligung von Phosphonester-Nachbargruppen bei Amindehydrierungen / Participation of Phosphonate Neighbour Groups with Dehydrogenations of Amines

1988 ◽  
Vol 43 (12) ◽  
pp. 1662-1671 ◽  
Author(s):  
Hans Möhrle ◽  
Wolfgang Vetter
Keyword(s):  
Reaction Mechanisms ◽  
Ester Hydrolysis ◽  
Hydrolysis Of

Abstract Aminomethanephosphonate. Mercury EDTA Dehydrogenation. Lactam. Formamide, Aminoalkylation Aminophosphonates 1-5 are dehydrogenated with mercury EDTA to the corresponding lactams 6-9 and surprisingly to the formamide derivative 10, The different rate of ester hydrolysis of these acylamine compounds, the steric requirements and the reaction mechanisms are dis-cussed.

scholarly journals Promiscuity of Carbonic Anhydrase II. Unexpected Ester Hydrolysis of Carbohydrate-Based Sulfamate Inhibitors

2011 ◽  
Vol 133 (45) ◽  
pp. 18452-18462 ◽  
Author(s):  
Marie Lopez ◽  
Hoan Vu ◽  
Conan K. Wang ◽  
Maarten G. Wolf ◽  
Gerrit Groenhof ◽  
...  
Keyword(s):  
Carbonic Anhydrase ◽  
Ester Hydrolysis ◽  
Carbonic Anhydrase Ii ◽  
Hydrolysis Of

scholarly journals Concurrent Neutral Ester Hydrolysis and Bromine Displacement in the Hydrolysis of Bromomethyl Chloroacetate.

1972 ◽  
Vol 26 ◽  
pp. 1326-1336
Author(s):  
Nils J. Cleve ◽  
Per Olav Kristiansen ◽  
Lars Henriksen ◽  
S. Liaaen-Jensen ◽  
Sigfrid Svensson
Keyword(s):  
Ester Hydrolysis ◽  
Hydrolysis Of
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