What is esterase

Disease states may also alter esterase activity. Abstract Esterases, hydrolases which split ester bonds, hydrolyse a number of compounds used as drugs in humans. Publication types Review. Furthermore, the research also concluded that the forces are hydrophobic. Esterase Function According to studies psychrophilic organisms that live in a cold environment where the climate does not fluctuate produce enzymes.

These are adapted to function and show high catalytic efficiency through low temperatures. This can be explained by two factors. One is the reduction in enthalpy with these enzymes.

This is due to the diminished number of protein-ligand interactions. It ensures substrate-binding as well as product release with a low energy barrier at lower temperatures.

Secondly, there is an entropy contrast between the enzyme-substrate complex and the apo-enzyme. This is due to the flexibility in confirmation during the substrate binding process. Grass Mix 1. Growth Hormone. Gynecological Cytology. H Hallux valgus.

HDL Cholesterol. Heel spur. Helicobacter pylori Breath Test. Helicobacter pylori Serology. Hemochromatosis Genotype. Hemoglobin Electrophoresis. Hepatitis B. Hepatitis C IgG. Herniated disc. Hiatal hernia. HLA B Hot zone. Howell-Jolly Body. HS Troponin T. Hyaline Casts. I Icterus. IGF 1. Iliotibial Band Friction Syndrome. Immunity and herd immunity.

Inhibin B. Insomnia acute or chronic. Ionized Calcium. Iron profile. Irritable bowel syndrome. K Karyotype. Ketones routine urine test. Kidney Cells. Kidney Disease nephropathy. L Lactiferous ducts. Lateral epicondylitis. LDL Cholesterol.

Leflunomide Metabolite. Leukocytes esterase. Leukocytes routine urine test. Liver profile. Lumbar Facet Syndrome. Lumbar osteoarthritis.

Lumbar sprain. Lying Aldosterone. Lying Renin. Lyme Disease. Lymphogranuloma venereum. M Macadamia Nuts. Maintenance of Wakefulness Test. Mean Corpuscular Hemoglobin. Mean Corpuscular Volume. Mean Platelet Volume. Medial epicondylitis. Meniscal lesion. Microbiological stool analysis by PCR. Mixed Casts. Molluscum contagiosum. Mono Test. Multiple Sleep Latency Test.

Mumps IgG and IgM. N N respirator mask. Nocturnal Paediatric Oximetry. Nucleated Red Blood Cells. O Oats. Obstructive sleep apnea. OI Cell Cold Agglutinin. Osmolality urination. In pectins, ferulic acid can be linked to galactose or arabinose in side chains. Ferulic acid thus obtained can be converted enzymatically into vanillin, a major flavor compound [ 25—27 ].

Feruloyl esterases have been isolated from a wide range of microorganisms [ 28—33 ]. Some of these esterases have been overexpressed in heterologous hosts and their properties are summarized in Table 2. In addition, the 2- O or 3- O positions of arabinose are often acetylated and the acetyl group can be also removed by the action of specific acetyl xylan esterases [ 34 , 35 ].

Properties of some of these recombinant enzymes are given in Table 2. Microbial carboxyl esterases are also involved in the catabolism of aryl esters as shown for an enzyme found in Acinetobacter sp. For a lactone-specific esterase from P. An application of considerable industrial interest is the mild removal of protecting groups as shown for a p -nitrobenzyl esterase from B.

As the enzyme is only weakly stable in dimethyl formamide, the esterase was improved by directed evolution see Section 4. Directed evolution also called evolutive biotechnology or molecular evolution is a technology developed in the early s to generate desired enzyme variants or, more recently, to evolve metabolic pathways. Usually, random mutagenesis of the gene encoding the protein is performed by error-prone PCR, leading to huge libraries of mutants.

Libraries thus created are then assayed by high-throughput techniques to identify improved variants, as the huge number of mutants cannot be analyzed by common analytical tools such as gas chromatography and high-performance liquid chromatography. These are too time-consuming and expensive and therefore spectrophotometric methods are frequently used, especially photometric and fluorimetric assays performed in microtiter plate-based formats in combination with high-throughput robot assistance.

Prerequisites for directed evolution are the availability of the gene s encoding the enzyme s of interest, a suitable usually microbial expression system, an effective method to create mutant libraries which are then assayed by a suitable screening or selection system. In contrast to rational protein design, the knowledge of the 3D structure of the enzyme and its mechanism of catalysis are not necessary. It should also be emphasized, that a mutant library, once created, can be stored and subjected to new screening rounds if a new problem to be solved comes up.

Detailed overviews about methods for directed evolution as well as various examples for its successful application can be found in a considerable number of recent reviews [ 11 , 38—48 ]. Due to its very recent development, only a few examples for the directed evolution of esterases can be found. In my own group, we succeeded in altering the substrate specificity of an esterase from P.

A sterically hindered 3-hydroxy ester not accepted as substrate by 20 wild-type hydrolases was stereoselectively hydrolyzed by a double-mutant of PFE generated using the mutator strain Epicurian coli XL1-Red [ 51 , 52 ]. The key to the identification of improved variants was an agar plate-assay system based on pH indicators, thus leading to a change in color upon hydrolysis of the ethylester. Parallel assay of replica-plated colonies on agar plates supplemented with the glycerol derivative of the 3-hydroxy ester was used to refine the identification, because only E.

Thus, in the next step, enantioselectivity of PFE was improved by directed evolution. Mutant libraries were created by error-prone PCR and by using the mutator strain. An extremely accurate determination of the enantioselectivity was achieved by using resorufin esters of R - or S phenylbutyric acid, which allowed measurement of fluorescence in microtiter plates avoiding problems with interfering compounds present in the culture medium [53].

Henke and U. Bornscheuer, unpublished. However, combinations of the best variants by site-directed mutagenesis gave no further improvement Figs.

It should be noted, that apparent E values E app determined in microtiter plates were quite close to E true values, which have been determined by gas chromatographic analysis of samples from resolutions of racemic mixtures of the corresponding ethylesters of 3-phenylbutyric acids. Here, competition between the two enantiomers is also included, whereas the microtiter plate-assay delivers only apparent E app values.

Mutants obtained by directed evolution and saturation mutagenesis showing enhanced enantioselectivity in the resolution of 3-phenylbutyric acid derivatives. MTP: E values E app determined in microtiter plates using the corresponding R - and S -resorufin ester [53] ; GC: E values E true calculated according to literature [56] from data determined by gas chromatographic analysis on a chiral column from samples obtained after esterase-catalyzed hydrolysis of R,S phenyl butyric acid ethylester [50].

Significantly higher increases in enantioselectivity were achieved for the resolution of methyl 3-bromomethylpropionate Fig. Using a homology model of PFE, Trp 29 and Phe were identified as positions for random mutagenesis. Libraries were then screened using Quick E [54] , which is based on hydrolysis of optically pure R - or S -enantiomers in separate wells of microtiter plates in the presence of suitable pH indicators.

The ratio of reaction rates for each enantiomer then yields E app. This is, so far, the highest selectivity ever achieved by directed evolution techniques U. Bornscheuer and R. Kazlauskas, unpublished , which now allows the synthesis of optically pure substrate and product of this compound. Even if an enzyme with the desired substrate specificity and enantioselectivity is identified, its efficient application in an industrial process is often hampered by unsatisfactory process performance and stability.

Directed evolution was successfully used to improve the stability and activity of an esterase from B. Unfortunately, the wild-type enzyme was only weakly active in the presence of dimethylformamide DMF , which must be added to dissolve the substrate. It was shown in this review, that a significant number of microbial carboxyl esterases has been discovered so far and many of them have been overexpressed, enabling, in principle, production on a commercial scale.

Moreover, our knowledge of their evolutionary relationships and the recent discovery of different consensus sequence motifs added considerably to our understanding of their functions.

The large diversity of reactions and substrates handled by esterases in nature is still poorly explored. In part, this is caused by their limited commercial availability and the extensive use of many lipases in biocatalysis.

However, modern methods of enzyme engineering — especially directed evolution — will certainly provide suitable carboxyl esterase variants with increased use in organic synthesis and other areas of application in the near future. The few examples of successfully evolved carboxyl esterases already show that this goal is indeed achievable. I am especially grateful to Prof. Bornscheuer, U. Wiley-VCH, Weinheim. Phytian, S. In: Biotechnology-Series, Vol. Patel, R. Marcel Dekker, New York.

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