Formate dehydrogenase product inhibition

Benzaldehyde can be produced from benzoyl formate with whole cells of Pseudomonas putida ATCC 12633 as biocatalyst119 201 (Fig. 16.6-5). Alternatively, but less effectively, mandelic acid can be used as starting material. A pH of 5.4 was found to be optimal for benzaldehyde accumulation. At this proton concentration, partial inactivation of the benzaldehyde dehydrogenase isoenzymes and activation of the benzoyl formate decarboxylase are reported. Fed-batch cultivation prevented substrate inhibition. In situ product removal is necessary to prevent product inhibition. 

To detect the presence of abortive ternary complexes, the kinetidst may raise the concentration of dissimilar substrate-product pairs (such as glucose-ADP and ATP-glucose-6-P in the hexokinase reaction, or acetaldehyde-NAD and ethanol-NADH in alcohol dehydrogenase reaction). This wiU lead to the inhibition of all exchanges irrespective of the kinetic mechanism, and provide useful information about the abortive complex formation (Wong Hanes, 1964 Wedler Boyer, 1972 Punch Allison, 1980, 2000). Nevertheless, product inhibition is stiU unrivaled as the means for detecting abortive complex formation. 

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