Mechanistic insight into allosteric activation of human pyruvate carboxylase by acetyl-CoA

Pyruvate carboxylase (PC) catalyzes the two-step carboxylation of pyruvate to produce oxaloacetate, play-ing a key role in the maintenance of metabolic homeostasis in cells. Given its involvement in multiple dis-eases, PC has been regarded as a potential therapeutic target for obesity, diabetes, and cancer. Albeit acetyl-CoA has been recognized as the allosteric regulator of PC for over 60 years, the underlying mechanism of how acetyl-CoA induces PC activation remains enigmatic. Herein, by using time-resolved cryo-electron microscopy, we have captured the snapshots of PC transitional states during its catalytic cycle. These struc-tures and the biochemical studies reveal that acetyl-CoA stabilizes PC in a catalytically competent conforma-tion, which triggers a cascade of events, including ATP hydrolysis and the long-distance communication between the two reactive centers. These findings provide an integrated picture for PC catalysis and unveil the unique allosteric mechanism of acetyl-CoA in an essential biochemical reaction in all kingdoms of life.

Automated summary

This study used cryo-electron microscopy to capture the intermediate states of pyruvate carboxylase (PC) during its catalytic cycle, revealing the mechanism of how acetyl-CoA induces PC activation.