Hexose phosphorylation by the ruminal bacterium Selenomonas ruminantium

Area of Science:

• Microbiology
• Biochemistry
• Bacterial Metabolism

Background:

• Selenomonas ruminantium is a key ruminal bacterium involved in carbohydrate metabolism.
• Understanding hexose phosphorylation pathways is crucial for elucidating nutrient utilization in ruminants.

Purpose of the Study:

• To investigate the phosphorylation of D-glucose and 2-deoxyglucose in three Selenomonas ruminantium strains.
• To determine the roles of phosphoenolpyruvate and ATP as phosphoryl donors in these processes.
• To characterize the enzymes and systems involved in hexose phosphorylation.

Main Methods:

• Hexose phosphorylation assays were performed on toluene-treated cells and cell extracts of S. ruminantium strains D, GA192, and H18.
• Phosphorylation was assessed using phosphoenolpyruvate and ATP as phosphoryl donors.
• Enzyme kinetics, including Lineweaver-Burk analysis, were used to study inhibitor interactions.

Main Results:

• Toluene-treated cells exhibited high hexose phosphorylation rates with both phosphoenolpyruvate and ATP, with phosphoenolpyruvate-dependent phosphorylation being pH-sensitive.
• Cell extracts showed significant phosphorylation of both hexoses by ATP, but negligible phosphorylation by phosphoenolpyruvate.
• 2-deoxyglucose competitively inhibited glucose phosphorylation, and glucose inhibited 2-deoxyglucose phosphorylation, indicating shared kinase activity.

Conclusions:

• The results suggest that glucose phosphorylation by phosphoenolpyruvate likely involves a membrane-associated phosphotransferase system in S. ruminantium.
• ATP-dependent phosphorylation of both glucose and 2-deoxyglucose is mediated by soluble kinases, with evidence of shared active sites.
• These phosphorylation pathways are common characteristics of the studied S. ruminantium strains.