Energy enzymatic transformation

A simple biodegradation model is one in which microorganisms are in contact with water containing a dissolved organic chemical that serves as the energy substrate. Because chemical uptake into a cell is followed by enzymatic transformation, biodegradation and uptake rates are equivalent in this model. It is... 

Compared to chemical synthesis, enzymatic transformation has several potential advantages, including its ecofriendly nature, low energy consumption, and reduced production cost. However, to date, there have been few reports on the enzymatic synthesis of a-KG. However, a-KG has been produced from L-glutamic acid by using amino acid deaminase. ... 

For bio-transformation processes, immobilised enzymes are often used because their activity persists over a longer period of time than that of free enzymes. The reduction of enzyme activity in enzymatic reactors is a consequence of energy dissipation by sparging and stirring, which is required for instance for oxygen transport or realisation of constant reaction conditions as regards temperature and pH. In the other hand low and high pH-values leads also to a decrease of enzyme activity and increase the stress sensitivity. 

In this chapter we have seen that enzymatic catalysis is initiated by the reversible interactions of a substrate molecule with the active site of the enzyme to form a non-covalent binary complex. The chemical transformation of the substrate to the product molecule occurs within the context of the enzyme active site subsequent to initial complex formation. We saw that the enormous rate enhancements for enzyme-catalyzed reactions are the result of specific mechanisms that enzymes use to achieve large reductions in the energy of activation associated with attainment of the reaction transition state structure. Stabilization of the reaction transition state in the context of the enzymatic reaction is the key contributor to both enzymatic rate enhancement and substrate specificity. We described several chemical strategies by which enzymes achieve this transition state stabilization. We also saw in this chapter that enzyme reactions are most commonly studied by following the kinetics of these reactions under steady state conditions. We defined three kinetic constants—kai KM, and kcJKM—that can be used to define the efficiency of enzymatic catalysis, and each reports on different portions of the enzymatic reaction pathway. Perturbations... 

Most nitroreductases found in bacteria to date fall into this type I category. Type I nitroreductive transformations may be limited by the first of two electron transfers in a tight sequence of one-electron transfers since the enzymatic rates correlate with the corresponding (ArN02) (see Eq. 14-32) values (Riefler and Smets, 2000). However, it has also been noted that the free energies of the one-electron and two-electron reductions correlate with one another, and therefore this thermodynamic data may not distinguish between the one- vs. two-electron possibilties (Nivinskas et al., 2001). 

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