Enzyme-Constrained Metabolic Model of Treponema pallidum Identified Glycerol-3-phosphate Dehydrogenase as an Alternate Electron Sink

Authors

• Nabia Shahreen, University of Nebraska-Lincoln
• Niaz Bahar Chowdhury, University of Nebraska-Lincoln
• Edward Stone, University of Nebraska-Lincoln
• Elle Knobbe, University of Nebraska-Lincoln
• Rajib Saha, University of Nebraska-LincolnFollow

ORCID IDs

Shahreen https://orcid.org/0000-0002-6461-6184

Saha https://orcid.org/0000-0002-2974-0243

Date of this Version

2025

Document Type

Article

Citation

mSystems (2025) 10(5)

doi: 10.1128/msystems.01555-24

Comments

Open access

License: CC BY 4.0

Abstract

Treponema pallidum, the causative agent of syphilis, poses a significant global health threat. Its strict reliance on host-derived nutrients and difficulties in in vitro cultivation have impeded detailed metabolic characterization. In this study, we present iTP251, the first genome-scale metabolic model of T. pallidum, reconstructed and extensively curated to capture its unique metabolic features. These refinements included the curation of key reactions such as pyrophosphate-dependent phosphorylation and pathways for nucleotide synthesis, amino acid synthesis, and cofactor metabolism. The model demonstrated high predictive accuracy, validated by a MEMOTE score of 92%. To further enhance its predictive capabilities, we developed ec-iTP251, an enzyme-constrained version of iTP251, incorporating enzyme turnover rate and molecular weight information for all reactions having gene-protein-reaction associations. Ec-iTP251 provides detailed insights into protein allocation across carbon sources, showing strong agreement with proteomics data (Pearson’s correlation of 0.88) in the central carbon pathway. Moreover, the thermodynamic analysis revealed that lactate uptake serves as an additional ATP-generating strategy to utilize unused proteomes, albeit at the cost of reducing the driving force of the central carbon pathway by 27%. Subsequent analysis identified glycerol-3-phosphate dehydrogenase as an alternative electron sink, compensating for the absence of a conventional electron transport chain while maintaining cellular redox balance. These findings highlight T. pallidum’s metabolic adaptations for survival and redox balance in nutrient-limited, extracellular host environments, providing a foundation for future research into its unique bioenergetics.