This latter possibility is what is shown in Figure 6 (F → G), with Aspa27 acting as the base, because it was found that the D27E mutant was particularly slow in the release of acetaldehyde from the enamine intermediate (45).
For the final step, release of acetaldehyde, deprotonation of the OH group of the hydroxyethyl-ThDP is required.
The E1p enzyme active site has evolved to prevent the proton-activated release of free acetaldehyde, which would represent an off-pathway misreaction for pyruvate dehydrogenase.
There seem to be a few things at work: gastric irritation; the effects of the acetaldehyde (the main breakdown product of alcohol), which is extremely toxic; tiredness.
We confirmed our results in the BY4741 mutants lacking ALD6, a member of the acetaldehyde dehydrogenase (ACDH) family that catalyzes conversion of acetaldehyde into acetic acid (Fig. 3A).
However, as pyruvate decarboxylase is also used to generate acetoin from acetaldehyde, the downregulation of PDC1 and PDC5 may result from disturbance of the acetaldehyde node.
The release of volatile ethylene and acetaldehyde characterizes the metabolic state and quality of fruit.
Pyruvate decarboxylase (PDC, EC 4.1.1.1), the subject of this study, catalyzes the conversion of pyruvate to acetaldehyde with release of carbon dioxide as part of the fermentation process that generates ethanol.
Acetaldehyde also triggers the release of histamine, which causes increased blood flow to the skin, leading to redness and itchiness.
The first step of the acetone synthesis is the acetaldehyde generation.
