engleski

Aldol addition of dihydroxyacetone to N-Cbz-3- aminopropanal

Aldol addition of dihydroxyacetone (DHA) to N-Cbz- 3-aminopropanal (aldehyde) was studied in this paper. The reaction was catalyzed by D-fructose-6- phosphate aldolase from genetically modified E. coli (FSA A129S). It is a reverse reaction whose equilibrium is shifted to the side of aldol production. A part of this research is related to alcohol dehydrogenase (ADH) and coenzyme regeneration methods, considering that the substrate in this reaction, aldehyde, can be obtained by ADH catalysis from the corresponding alcohol. The reaction kinetics was determined in the case of aldol addition of DHA to aldehyde, but not for the reverse reaction. The initial reaction rate method was used. The influence of DHA and aldehyde was examined and from the gathered data kinetic parameters were estimated (Vm1, Km, DHA, Km, aldehyde). Since it was stated that a part of this research is related to ADH and coenzyme regeneration methods, the influence of different compounds that appear in the coenzyme regenerating systems were tested. It was important to see which compounds were inhibiting and which were not, because the choice of the regenerating method depends on that as well. From these data inhibition constants were estimated. The NAD+ regenerating systems investigated were: pyruvate → lactate, D-glucono- 1, 5-lactone → glucose and acetone → isopropanol. Aldol addition of DHA to N- Cbz-3-aminopropanal was carried out in the batch reactor at equimolar conditions. 80% of substrate conversion was achieved. A repetitive batch experiment was also carried out to examine the operational stability of aldolase.

aldolase; N-Cbz-3-aminopropanal; kinetic model; alcohol dehydrogenase

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