Pyruvate Transformations

BioFiles 2007, 2.6, 10.

BioFiles 2007, 2.6, 10.

Depending on the environmental conditions, e.g. whether oxygen is present or not, pyruvate, a product of glucose metabolism, can undergo different biotransformations as shown in Figure 2. Under reductive conditions, e.g. in the absence of oxygen, pyruvate (1) can be either reduced to lactate (2) or ethanol (5). The well-known formation of L-lactate from pyruvate in muscles during intense physical activity is catalyzed by lactate dehydrogenase (LDH) which requires NADH as a reducing coenzyme.

Figure 2. Pyruvate Biotransformations.

The fundamental process by which alcoholic beverages are made is through the conversion of pyruvate to ethanol by yeast under anaerobic conditions.

Pyruvate (1) is in the first step decarboxylated to acetaldehyde (4) using thiamindiphosphate as a cofactor.

In the second step, acetaldehyde is then reduced to ethanol (5) with NADH as reducing coenzyme, also transferring the pro-R hydrogen from NADH to acetaldehyde.

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