Proline competitive production

As first espoused by Knowles and Albery, the limiting selective pressure on enzymatic function is the diffusion-controlled limit by which substrates bind and products dissociate [7]. In the case of triose phosphate isomerase [8], ketosteroid iso-merase [9], mandelate racemase [10], and proline racemase [11], the energies of various transition states on the reactions coordinates have been quantitated, with the result that the free energies of the transition states for the proton transfer reactions to and from carbon are competitive with those for substrate association/ product dissociation. However, as discussed in later sections, the energies of the... 

Oversaturation, mentioned above, is another phenomenon resulting from the competition between solvent catalyzed conversion of enzymic forms and the conversion via substrate racemization [82]. A consequence of this competition is that the net rate of racemization decreases, under reversible conditions, as the concentration of a proline increases. The loss of productivity in the racemization manifold is due to the product form of the enzyme binding substrate, and the substrate form of the enzyme binding product (i.e., substrate inhibition). 

When initial concentrations of proline from 16 to 190 mM were used, however, a different pattern was observed. Although the initial velocities were the same, the half-times for approach to equilibrium divided by the initial substrate concentrations increased with increasing substrate concentrations. This phenomenon, which was called oversaturation, results from developing noncompetitive product inhibition during the reaction. If the developing product inhibition were competitive, the normalized time courses would be identical for all saturating substrate levels. 

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