Recombinant Yersinia pestis bv. Antiqua 6-phosphofructokinase (pfkA)

What is Yersinia pestis bv. Antiqua 6-phosphofructokinase (pfkA) and what is its role in bacterial metabolism?

PfkA (6-phosphofructokinase) is a key glycolytic enzyme that catalyzes the phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate, a rate-limiting step in glycolysis. In Y. pestis, pfkA plays a role in glucose metabolism during host infection. Research indicates that Y. pestis relies on carbohydrates as its main carbon and energy source during successful colonization of mammalian hosts . The enzyme is identified by Uniprot accession number A9R6A3 in the Y. pestis bv. Antiqua strain .

The enzyme functions as:

• EC 2.7.1.11 (official enzyme classification)

• Alternative names: Phosphofructokinase, Phosphohexokinase

What are the optimal storage and handling conditions for recombinant Y. pestis pfkA?

For successful experimental use of recombinant Y. pestis pfkA, researchers should adhere to these storage and handling conditions:

Shelf life details:

• Liquid form: 6 months at -20°C/-80°C

• Lyophilized form: 12 months at -20°C/-80°C

These conditions are critical for maintaining enzymatic activity and structural integrity during experimental procedures.

What are the recommended reconstitution protocols for recombinant Y. pestis pfkA?

The optimal reconstitution protocol involves:

• Briefly centrifuge the vial prior to opening to bring contents to the bottom

• Reconstitute the protein in deionized sterile water to a concentration of 0.1-1.0 mg/mL

• Add glycerol to a final concentration of 5-50% (default recommendation is 50%)

• Aliquot for long-term storage at -20°C/-80°C

This protocol ensures maximum retention of enzymatic activity and prevents protein degradation during storage and experimental use.

How can researchers experimentally determine the kinetic parameters of Y. pestis pfkA?

While specific protocols are not detailed in the search results, recommended approaches for characterizing pfkA kinetic parameters include:

• Spectrophotometric coupled enzyme assays: Monitor NADH oxidation at 340 nm by coupling pfkA reaction to auxiliary enzymes (aldolase, triosephosphate isomerase, and glycerol-3-phosphate dehydrogenase)

• Substrate concentration series: Determine Km and Vmax values by measuring reaction rates at varying concentrations of fructose-6-phosphate and ATP

• Allosteric regulation analysis: Assess effects of known phosphofructokinase regulators (ATP, AMP, PEP, citrate) on enzyme activity

• pH and temperature optima determination: Measure activity across pH and temperature ranges to establish optimal conditions

These methodologies allow researchers to characterize the catalytic efficiency and regulatory properties of Y. pestis pfkA compared to those from other organisms.

How does pfkA contribute to Y. pestis virulence and metabolic adaptation during infection?

Interestingly, research reveals complex relationships between pfkA, metabolism, and virulence:

• Despite pfkA's role in glycolysis, deletion of pfkA did not affect Y. pestis virulence

• This finding is part of a broader observation that while Y. pestis relies on carbohydrates during host colonization, the complete glycolysis pathway is not essential for this process

• The terminal part of glycolysis does appear essential, as a gpmA mutant was completely outcompeted in vivo

• Y. pestis appears to shift toward anaerobic respiration during infection, as mutants lacking DMSO reductase (DmsABC) and glycerol-3P dehydrogenase (GlpABC) were outcompeted in virulence screening

These findings suggest Y. pestis possesses metabolic flexibility during infection, with redundant pathways that can compensate for the loss of pfkA function.

What is the relationship between carbohydrate metabolism and Y. pestis survival in the host environment?

Y. pestis demonstrates specific adaptations in carbohydrate metabolism during host infection:

• Carbohydrates, particularly glucose, gluconate, and to a lesser extent maltose, are important carbon sources during mammalian host colonization

• The bacterium shifts to anaerobic respiration or fermentation when colonizing the host

• The TCA cycle is down-regulated in vivo, suggesting reduced aerobic metabolism

• Pyruvate production appears crucial, as mutants lacking pyruvate dehydrogenase AceEF were unable to produce fatal plague

These adaptations suggest Y. pestis has evolved specialized metabolic strategies that optimize survival in the host environment, potentially using alternative pathways that bypass conventional glycolysis.

How can structural biology approaches enhance our understanding of Y. pestis pfkA function?

Advanced structural biology techniques can provide critical insights into pfkA function:

These approaches could identify unique structural features that might explain pfkA's role in Y. pestis metabolism during infection.

What experimental considerations are crucial when studying pfkA in the context of host-pathogen interactions?

When investigating pfkA's role in host-pathogen interactions, researchers should consider:

• In vivo versus in vitro conditions: Y. pestis metabolism differs significantly between laboratory conditions and during infection

• Redundant metabolic pathways: The finding that pfkA deletion doesn't affect virulence despite glucose being important suggests redundant pathways

• Oxygen availability: Y. pestis shifts to anaerobic respiration during infection , making oxygen control crucial in experimental systems

• Carbon source availability: Experimental media should reflect physiologically relevant carbon sources, as Y. pestis relies on specific carbohydrates during infection

• Combinatorial genetic approaches: Single gene deletions may not reveal phenotypes due to redundancy; multiple deletions might be necessary to uncover pfkA's role

These considerations help design experiments that more accurately reflect the complex metabolic adaptations of Y. pestis during infection.

How does Y. pestis pfkA compare with phosphofructokinases from other bacterial pathogens?

While the search results don't provide direct comparative information, several inferences can be made:

• Y. pestis evolved relatively recently from Y. pseudotuberculosis, which also possesses pfkA , suggesting these enzymes share high sequence similarity

• Significant genome changes occurred during Y. pestis evolution, including both genome decay and horizontal gene acquisition

• Y. pestis demonstrates unusual metabolic adaptations during infection, including the apparent non-essentiality of pfkA despite the importance of glucose metabolism

A comprehensive comparative analysis would require sequence alignments, phylogenetic analysis, and biochemical characterization of pfkA from multiple species to identify specific differences that might reflect adaptation to different ecological niches.

What insights can metabolic enzyme studies provide about Y. pestis evolution and host adaptation?

Studying metabolic enzymes like pfkA provides valuable evolutionary insights:

• Metabolic adaptation during pathogen evolution: Y. pestis underwent significant metabolic adaptations during its evolution from Y. pseudotuberculosis, including shifts toward anaerobic metabolism during infection

• Horizontal gene transfer: While pfkA is likely a vertically inherited core gene, the research highlights the importance of horizontally acquired genes like ypmt1.66c in Y. pestis virulence

• Host environment adaptation: The non-essentiality of pfkA despite glucose being important suggests Y. pestis evolved metabolic flexibility to adapt to different host environments

• Minimal essential gene set: The research notes that "only a small set of genes (including horizontally acquired and uncharacterized sequences) are required for these infectious processes"

These findings contribute to our understanding of how metabolic pathways evolve during the emergence of highly virulent pathogens like Y. pestis.