Pyruvic acid (Pyruvate)
Pyruvic acid
Japanese: ピルビン酸
The final product of glycolysis. From here, metabolic pathways diverge into fermentation (alcohol, lactic acid) and respiration (TCA cycle)—a metabolic crossroads.
Pyruvate is a three-carbon organic acid, the final product of glycolysis. What happens to this molecule next determines the fork between fermentation and respiration.
With oxygen, pyruvate is converted to acetyl-CoA, enters the TCA cycle, and is fully oxidized to produce abundant ATP. Without oxygen, yeast converts it to ethanol via acetaldehyde, while lactic acid bacteria convert it to lactic acid.
Pyruvate is a metabolic 'hub.' Different pathways are chosen depending on microbial species and environmental conditions, yielding different products. Alcohol, lactic acid, acetic acid—the diversity of fermented foods lies at the end of multiple roads branching from this hub.