Chemical modification of enzyme

J. Eyzaguirre, ed., Chemical modification of enzymes, active site studies, Ellis Norwood series in biochemistry, Ellis Horwood Ltd. (1987). 

DeSantis G, Jones JB (1999) Chemical modification of enzymes for enhanced functionality. Curr Opin Biotechnol 10 324-330... 

The following new trends in enzymatic synthesis can be delineated the development of new enzymatic reactions enzyme immobilization and stabilization the use of organic solvents and two phase systems site-directed mutagenesis chemical modification of enzymes antibody catalysis catalysis by RNA and DNA de novo design ofbiocatalists employment of recombinant DNA for production of enzymes and use computational and combinatorial methods... 

Reversible chemical modification of enzymes, which was discovered in 1955 by Edmond Fischer and Edwin Krebs [58], is a more prevalent mechanism for cellular signaling switching. Fischer and Krebs showed that enzymes can be turned from an inactive form to an active form via phosphorylation of certain residues of the protein. Enzymes that catalyze phosphorylation (addition of a phosphate group coupled with ATP or GTP hydrolysis) are called protein kinases. Enzymes that catalyze dephosphorylation (which is not the reverse reaction of the phosphorylation) are called phosphatases. For example, a protein tyrosine phosphatase is an enzyme that catalyzes the removal of a phosphate group from a tyrosine residue in a phosphorylated protein [57],... 

Eyzaguirre, J. (Ed.) (1987) Chemical Modification of Enzymes Active Site Studies. Ellis Horwood,... 

It is illustrative to mention that the first chemical modification of enzymes was earlier than the discovery of site-directed mutagenesis. In 1966 a chemical approach for converting the active site serine-derived hydroxyl group present in subtilizin to a thiol was reported [476,477]. Since then, chemical modification has been demonstrated to be a rapid and inexpensive approach for enhancing and modifying the analytical properties... 

Irrespective of the potential of the random chemical modification, this tool usually renders a mixture of semis5mthetic enz5nnes as consequence of their inherent low selectivity and, in some cases, low efficiency. Additionally, the yield and accuracy of these modifications in hmited chemical functional groups is not always predictable. Consequently, and in order to exploit all the possibilities of the chemical modification of enzymes, it is necessary to achieve specific chemical reactions of the target enzyme with high specificity and efficiency. 

Richter ER (1993) Biosensors applications for dairy food industry. J Dairy Sci 76(10) 3114-3117 Roberts S (1998) Preparative biotransformations the employment of enzymes and whole-cells in synthetic organic chemistry. J Chem Soc Perkin Trans 1 157-170 Roberts S (2000) Preparative biotransformations. J Chem Soc Perkin Trans 1 611-633 Roig M, Kennedy J (1992) Perspectives of chemical modification of enzymes. Critic Rev Biotechnol 12 391 12... 

Although the site-directed mutagenesis and catalytic antibody technique are useful genetic methods, chemical modification of enzymes remains a valuable tooi for protein engineering. The latter approaches are divided into... 

Chemical Modification of Lipases. The chemical modification of enzymes involving the formation of covalent bonds are a major tool for elucidating the mechanisms of enzymatic catalysis [496 98]. These investigations were aimed primarily at defining those amino acids which participate in catalysis and those which are important in substrate binding. Furthermore, the properties of the enzyme such as solubility, pH optimum, inhibition patterns, and the relative reactivity towards different substrates - the specificity - can be varied by chemical modification. More recently, it was also shown that the enantioselectivity of a lipase may also be improved by covalent modification [499-501] (compare Scheme 2.72 and Table 2.2). 

Site-directed chemical modification of enzymes using group-specific reagents was established mainly during the 1960s aiming at the elucidation of enzyme strucmres and mechanisms [458,459] rather than for the creation of biocatalysts with a better performance. In other words, enzyme modification has been developed more as... 

The chemical modification of enzymes to solubilize them in completely nonaqueous, nonpolar media has been attempted with some success. All methods of chemical modification of enzymes share the same principle the attachment of amphipatic reagents to the polar groups on the exterior of the native protein to stabilize the enzyme against denaturation by hydrophobic organic solvents. Depending on the nature of the interaction between the enzyme and the solubilizing agent, chemical modifications of enzymes can be classified into covalent and noncovalent ones. Various methods of enzyme modification adopted are summarized in Table 4.4. 

DeSantis, G., and J. B. Jones. 1999. Chemical Modification of Enzymes for Enhanced Functionality. Current Opinion in Biotechnology 10 (4) 324-330. 

Chemical modification of enzymes is frequently correlated with changes in levels of activity. Mammalian RNA polymerase II subunits are phosphorylated in vivo (Bell et al., 1977 Dahmus, 1981a). Labeling of HeLa cells with results in phosphate incorporation into pol II polypeptides of 240,000, 214,000, and 20,500 daltons (Dahmus, 1981a). Purified pol II is a substrate for both casein kinase I and II and for the cyclic AMP independent nuclear protein kinase NIL The... 

Holzer, H., and Duntze, W., 1971, Metabolic regulation by chemical modification of enzymes, Annu. Rev. Biochem. 40 345. 

Despite the extensive use to which photochemical oxidations of proteins have been put very little attention has been given to identifying the end products of the photoreactions. Apart from methionine which is converted to methionine sulfoxide and more slowly to its sulfone, the fate of the other amino acid residues of irradiated proteins remains largely unknown. On the basis of limited chemical studies, it is clear, however, that photoreactions usually lead to a mixture of products. The multiplicity of products formed by photooxidation of enzymes will undoubtedly limit the utility of the technique. There are in fact numerous examples from work dealing with the chemical modification of enzymes which indicate that modification of a particular residue with different chemical reagents leads to enzyme derivatives with different biological and physico-chemical properties. 

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