Regulation of Yeast Pyruvate Kinase by Ultrasensitive Allostery Independent of Phosphorylation

• Published in: Molecular cell Vol. 48; no. 1; pp. 52 - 62
• Main Authors: Xu, Yi-Fan, Zhao, Xin, Glass, David S., Absalan, Farnaz, Perlman, David H., Broach, James R., Rabinowitz, Joshua D.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 12.10.2012
• Subjects: Allosteric properties; Allosteric Regulation; case studies; Environmental changes; Ethanol; Fructose-1,6-diphosphate; Fructosediphosphates - metabolism; Genes, Fungal; genetically engineered microorganisms; Glucose; Glucose - metabolism; Isoenzymes; Isoenzymes - genetics; Isoenzymes - metabolism; isozymes; Metabolome; Phosphoenolpyruvate - metabolism; Phosphorylation; Point Mutation; Pyruvate kinase; Pyruvate Kinase - genetics; Pyruvate Kinase - metabolism; Saccharomyces cerevisiae - enzymology; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Transcriptome; yeasts
• ISSN: 1097-2765; 1097-4164
• DOI: 10.1016/j.molcel.2012.07.013

Allostery and covalent modification are major means of fast-acting metabolic regulation. Their relative roles in responding to environmental changes remain, however, unclear. Here we examine this issue, using as a case study the rapid decrease in pyruvate kinase flux in yeast upon glucose removal. The main pyruvate kinase isozyme (Cdc19) is phosphorylated in response to environmental cues. It also exhibits positively cooperative (ultrasensitive) allosteric activation by fructose-1,6-bisphosphate (FBP). Glucose removal causes accumulation of Cdc19’s substrate, phosphoenolpyruvate. This response is retained in strains with altered protein-kinase-A or AMP-activated-protein-kinase activity or with CDC19 carrying mutated phosphorylation sites. In contrast, yeast engineered with a CDC19 point mutation that ablates FBP-based regulation fail to accumulate phosphoenolpyruvate. They also fail to grow on ethanol and slowly resume growth upon glucose upshift. Thus, while yeast pyruvate kinase is covalently modified in response to glucose availability, its activity is controlled almost exclusively by ultrasensitive allostery. ► Glucose removal in yeast rapidly inactivates pyruvate kinase ► This response does not depend on kinase signaling ► Instead it relies on ultrasensitive allosteric activation by fructose bisphosphate ► This allostery is advantageous in gluconeogenic and oscillating glucose conditions