Enzyme catalyzed reaction 514 INDEX

The relationship between the geometry of the saddle point of index one (SPi-1) and the accessibility to the quantum transition states cannot be proved, but it can be postulated [43,172], To some extent, invariance of the geometry associated with the SPi-1 would entail an invariance of the quantum states responsible for the interconversion. Thus, if a chemical process follows the same mechanism in different solvents, the invariance of the geometry of the SPi-1 to solvent effects would ensure the mechanistic invariance. This idea has been proposed by us based on computational evidence during the study of some enzyme catalyzed reactions [94, 96, 97, 100-102, 173, 174, 181-184],... 

Symbolized by Q, the quality index is a parameter used in studying the stereochemical nature of a particular enzyme-catalyzed reaction using chiral [ O, 0, 0] phosphoric monoesters. This parameter, which is dependent on the fractional content, allows the investigator a means to assess the reliability of the study(ies). 

Many attempts have been made to correlate the enantioselective properties of enzymes with structure and/or process conditions [61, 70-73]. Attempts to correlate the effect of a particular medium on the enantioselectivity of an enzyme-catalyzed reaction with physico-chemical descriptors of the solvent have also been reported by a number of groups [22, 59, 64, 74]. Correlations with solvent size [75], dielectric constant [59], polarizability, electron pair acceptance index [76], logP [17],... 

This chapter demonstrates the usefulness of BasicBiochemDataS (1). In the future this database can be extended and many reactions can be added to this list of 229 enzyme-catalyzed reactions. At the present time Af is known for the species of 94 reactants. Future measurements of A, // ° and enthalpies of dissociation of weak acids will be used to calculate Af H° of species of more reactants so that the effects of temperature can be calculated for more reactions. When more heat capacities of species have been determined, it will be possible to make calculations of K over wider ranges of temperature. BasicBiochemDataS contains functions of pH and ionic strength for A, G ° of these 229 enzyme-catalyzed reactions so that A, G ° and A, A h can be calculated for these reactions at 298.15 K, pHs in the range 5 to 9, and ionic strengths in the range zero to 0.35 M. The index given in the Appendix lists the EC numbers for reactions that involve these 167 reactants. 

For biotechnological synthesis, there is a superb database containing information on miaobial biocatalytic reactions and biodegradation pathways for primarily xenobiotic, chemical componnds. It is called the University of Minnesota Biocatalysis/Biodegradation Database (UM-BBD) at can be fonnd at http //nmbbd.ahc.umn.edu/search/index.html. The goal of the UM-BBD is to provide information on microbial enzyme-catalyzed reactions that are important for biotechnology. 

Enzymes are excellent catalysts for two reasons great specificity and high turnover rates. With but few exceptions, all reac tions in biological systems are catalyzed by enzymes, and each enzyme usually catalyzes only one reaction. For most of the important enzymes and other proteins, the amino-acid sequences and three-dimensional structures have been determined. When the molecular struc ture of an enzyme is known, a precise molecular weight could be used to state concentration in molar units. However, the amount is usually expressed in terms of catalytic activity because some of the enzyme may be denatured or otherwise inactive. An international unit (lU) of an enzyme is defined as the amount capable of producing one micromole of its reaction product in one minute under its optimal (or some defined) reaction conditions. Specific activity, the activity per unit mass, is an index of enzyme purity. 

CONTENTS Preface. Patrick S. Mariano. Recent Advances In Light-Induced Election Transfer Involving Inorganic Systems. Nick Serpone, Rita Terzian and Jean Marie Hermann. Photoinduced Electron Transfer in Dye-Polymer Conjugates, Guilford Jones. Sequential Electron Transfer in Oxidation Reactions Catalyzed by Cytochrome P-450 Enzymes, Peter Guengerich and Timonty L Macdonald. Inner Shell Relaxation Effects on Electron Transfer Reactions of Amino Centered Systems, Stephen F. Nelsen. Index. s s... 

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