- Comparative study of substrate- and stereospecificity of penicillin G amidases from different sources and hybrid isoenzymes
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Four natural pencillin G amidase variants from different sources and two genetically constructed hybrid enzymes were produced and purified to homogeneity. The specificity constants of one enzyme (E. coli) were found to differ six orders of magnitude for hydrolytic transformations within a wide range of substrates. The substrate specificity of the homologous penicillin amidases was found to differ less than one order of magnitude for hydrolysis of the most specific and up to two orders of magnitude for the less specific substrates. The S′1-substrate specificity in hydrolytic and transfer reactions (studied mainly with the E. coli enzyme) varied more than three orders of magnitude for the different substrates. The penicillin amidases were found to be R-specific in the S1-binding site and S-specific in the S′1-binding site. The S1-stereoselectivity differs less than one order of magnitude for the different variants. The S′1-stereoselectivity is more pronounced, increases with nucleophile specificity, and was found to differ up to three orders of magnitude in transfer reactions for the enzyme from E. coli. The observed variation of enatioselectivity for different penicillin amidases and one substrate can also be achieved by changes in temperature. Comparison of substrate-and stereospecificity of penicillin amidases from different sources and hybrid isoenzymes suggests that similar changes can be expected for enzyme variants derived by rational protein design or directed evolution.
- Galunsky, Boris,Lummer, Karsten,Kasche, Volker
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Read Online
- Exponential diagnostic signal amplification via dendritic chain reaction: The dendritic effect of a self-immolative amplifier component
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Signal amplification techniques are commonly used to boost diagnostic signals. We have recently developed a new approach for exponential signal amplification obtained through a distinctive dendritic chain reaction. Here we report evaluation of the effect of the self-immolative dendritic amplifier component on the signal amplification. Four dendrons with various numbers of end-units were evaluated for the ability to produce exponential signal amplification through self-immolative disassembly pathways. The dendron composed of a first-generation platform with three end-units exhibited the best characteristics with rapid disassembly rate and good stability under aqueous conditions. This study demonstrates the efficiency of molecules based on dendritic structures.
- Karton-Lifshin, Naama,Shabat, Doron
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supporting information; scheme or table
p. 386 - 393
(2012/03/22)
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- Sulfhydryl-based dendritic chain reaction
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A new dendritic chain reaction probe system was demonstrated to produce exponential signal amplification for the detection of sulfhydryl compounds.
- Sella, Eran,Weinstain, Roy,Erez, Rotem,Burns, Noah Z.,Baran, Phil S.,Shabat, Doron
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supporting information; experimental part
p. 6575 - 6577
(2010/10/21)
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- Two-component dendritic chain reactions: experiment and theory
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New analytical diagnostic techniques that are based on signal-amplification mechanisms could significantly improve the sensitivity of detection of various analytes. We have developed a new approach to achieving exponential amplification of a diagnostic signal through a two-component dendritic chain reaction. The chain reaction generated the analyte of interest and thereby initiated additional diagnostic cycles. The system was designed for the detection of hydrogen peroxide and produced significantly larger intensity of diagnostic signal than a classic probe. In addition, a mathematical model that simulates the disassembly kinetics of one-component and two-component reactions was developed and shown to correlate well with the observed experimental data. The modularity and flexibility of a two-component detection system should allow extension to the detection of other analytes.
- Seila, Eran,Lubelski, Ariel,Klafter, Joseph,Shabat, Doron
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supporting information; experimental part
p. 3945 - 3952
(2010/05/15)
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- The pyridinone-methide elimination
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The quinone-methide elimination is a common, efficient methodology used in linkers designed to undergo self-fragmentation. Here, for the first time, we demonstrate this elimination in a pyridine ring system. Under physiological conditions, a compound cons
- Perry-Feigenbaum, Rotem,Baran, Phil S.,Shabat, Doron
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scheme or table
p. 4825 - 4828
(2010/02/16)
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- The azaquinone-methide elimination: Comparison study of 1,6- and 1,4-eliminations under physiological conditions
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The azaquinone-methide elimination is a powerful and efficient reaction useful for disassembly of spacers in prodrug systems. We and others have used the spacer-technique to develop dendritic and polymeric self-immolative molecular systems that can disass
- Erez, Rotem,Shabat, Doron
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scheme or table
p. 2669 - 2672
(2009/02/02)
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- A convenient copper-catalyzed direct animation of nitroarenes with 9-alkylhydroxylamines
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O-Alkylhydroxylamines, particularly O-methylhydroxylamine, aminate nitroarenes in the presence of a strong base and a copper catalyst to give aminonitroarenes in good yields, ortho- or para-Animation with respect to the nitro group takes place, and in some cases the ortho-aminated product is preferentially obtained. With 3-substituted nitrobenzenes where the substituent has a lone pair of electrons, preferential amination occurs at the 2-position to give the sterically most congested 3c-f, 14 and 22g.
- Seko, Shinzo,Miyake, Kunihito,Kavvamura, Norio
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p. 1437 - 1444
(2007/10/03)
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- Selective deprotection of phthalyl protected amines
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Phthalyl amidase selectively deprotects phthalimido groups under very mild aqueous conditions in a one-pot reaction to produce phthalic acid and the free amine. The enzyme has been shown to deprotect several primary amines of distinctly different structure, and exhibits chiral selectivity when the substrate contains extensive β-branching. The enzyme has a definite requirement for ortho positioning of the functional groups on a fixed axis of rotation.
- Costello, Colleen A.,Kreuzman, Adam J.,Zmijewski, Milton J.
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p. 7469 - 7472
(2007/10/03)
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- Bisazo brown reactive dye
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A brown reactive dye represented by a free acid of the formula, STR1 wherein R is a hydrogen atom or a C1 to C4 alkyl group, X is --SO2 CH2 CH2 Cl, --SO2 CH=CH2, --SO2 CH2 CH2 OSO3 H or --SO2 CH2 CH2 OPO3 H2, rings A, B and C are each a benzene or naphthalene ring which may have other substituent, m is 0 to 3 and n is 0 to 1. This dye is suitable for dyeing cellulose fibers brown to afford dyeings superior in fastnesses, acid stability, build-up property and level dyeing property.
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- Catalysis of Anilide Hydrolysis by Poly(ethylenimine) Derivatives
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Amide hydrolysis in 4-nitro-3-carboxytrifluoroacetanilide (1) is catalyzed by poly(ethylenimines).The rate-controlling step is the formation of a tetrahedral intermediate, breakdown of which is catalyzed by the conjugate acid and base forms of the amine g
- Suh, Junghun,Klotz, Irving M.
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p. 2373 - 2378
(2007/10/02)
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- Azo dyestuffs
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Azo dyestuffs, which in the acid form, are represented by the formula: wherein A is an aromatic radical, M is a 1,4-benzene radical which may be substituted, E is the residue of a coupling component which is free from azo groups, At least one of A and M containing a phosphonic acid group, and the metal complexes of those having a metallisable group are reactive dyes suitable for use in the process of German OLS No. 2324809.
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