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Pirin regulates pyruvate catabolism by interacting with the pyruvate dehydrogenase E1 subunit and modulating pyruvate

Po-Chi Soo1, Yu-Tze Horng, Meng-Jiun Lai

  • 1Department of Clinical Laboratory Sciences and Medical Biotechnology, National Taiwan University College of Medicine, No. 1 Chan-Der Street, Taipei 100, Taiwan, Republic of China.

Journal of Bacteriology
|September 19, 2006
PubMed

Insights

The Serratia marcescens pirin (pirin(Sm)) gene interacts with and inhibits pyruvate dehydrogenase (PDH) enzyme activity. Pirin(Sm) mutation boosts cellular ATP and tricarboxylic acid (TCA) cycle activity, influencing pyruvate metabolism.

Area of Science:

  • Microbiology
  • Biochemistry
  • Molecular Biology

Background:

  • Pirin protein is conserved across species and involved in diverse biological processes.
  • Its function in prokaryotes, particularly in bacteria like Serratia marcescens, is largely uncharacterized.
  • Understanding pirin's role in bacterial metabolism is crucial for deciphering its broader biological significance.

Purpose of the Study:

  • To investigate the function of the pirin(Sm) gene in Serratia marcescens.
  • To identify pirin(Sm) interacting partners within S. marcescens.
  • To elucidate the regulatory role of pirin(Sm) in pyruvate metabolism.

Main Methods:

  • Protein pull-down assays and bacterial two-hybrid systems to identify pirin(Sm) interactors.
  • Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and electrospray ionization-tandem mass spectrometry (ESI-MS/MS) for protein identification.
  • Enzyme activity assays for pyruvate dehydrogenase (PDH) E1 subunit and the PDH complex.
  • Construction and analysis of a pirin(Sm) mutant using insertion-deletion homologous recombination.

Main Results:

  • The pirin(Sm) gene product interacts with the pyruvate dehydrogenase (PDH) E1 subunit.
  • pirin(Sm) inhibits both PDH E1 subunit activity and overall PDH enzyme complex activity in S. marcescens CH-1.
  • Mutation of the pirin(Sm) gene led to significant increases in PDH E1 activity (250%), PDH complex activity (140%), and cellular ATP concentration (220%).
  • The pirin(Sm) mutant exhibited an elevated NADH/NAD+ ratio, indicating enhanced tricarboxylic acid (TCA) cycle activity.

Conclusions:

  • The pirin(Sm) gene acts as a negative regulator of pyruvate catabolism to acetyl coenzyme A by inhibiting PDH enzyme complex activity.
  • pirin(Sm) plays a key role in directing pyruvate metabolism towards either the TCA cycle or fermentation pathways in S. marcescens.
  • These findings reveal a novel regulatory mechanism for central carbon metabolism in bacteria.

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