Pyruvate decarboxylase, advantage

An alternative method for driving the reaction equilibrium of transaminations was developed by Hohne et al. (Figure 14.44) [65]. Alanine served as the amine donor, and pyruvate decarboxylase was used to remove the pyruvate coproduct by decarboxyl ation to acetaldehyde. An advantage of pyruvate decarboxylase over lactate dehydro genase is that it requires no cofactor recycling system, and the high volatility of the coproducts allows for the desired shift of equilibrium. 

Though use of isolated purified enzymes is advantageous in that undesirable byproduct formation mediated by contaminating enzymes is avoided [37], in many industrial biotransformation processes for greater cost effectiveness the biocatalyst used is in the form of whole cells. For this reason baker s yeast, which is readily available, has attracted substantial attention from organic chemists as a catalyst for biotransformation processes. One of the first commercialized microbial biotransformation processes was baker s yeast-mediated production of (R)-phenylacetyl carbinol, where yeast pyruvate decarboxylase catalyzes acyloin formation during metabolism of sugars or pyruvate in the presence of benzaldehyde [38]. 

Creighton and Rose (45) have explored the route shown in Scheme 7 to synthesize chiral pyruvate. The method takes advantage of the fact that pyruvate kinase decarboxylates oxalacetate with retention of configuration. The requisite labeled oxalacetates were prepared as shown from the appropriately labeled L-malates, available from equilibration with fumarase in either deuterated or tritiated water. This method is convenient for the preparation of small amounts of chiral acetate but suffers from the low oxalacetate decarboxylase activity of pyruvate kinase. 

---