Characterization of acid phosphatase activities in the equine pathogen Streptococcus equi.

This study investigated acid phosphatases, enzymes that break down phosphomonoesters at acidic pH, present in the bacterial genus Streptococcus, particularly strains that cause diseases in horses. The researchers found that these bacteria have two types of acid phosphatase activities and one of them is likely equivalent to the LppC enzyme present in a similar bacterial species.

Looking Into Acid Phosphatase Activities

• The researchers focused on acid phosphatases, enzymes that break down phosphomonoesters in acidic conditions. These enzymes have a range of roles in different physiological contexts.
• They focused on two strains of Streptococcus equi, a type of bacteria that causes diseases in horses. Specifically, they looked at Streptococcus equi subsp. equi and Streptococcus equi subsp. zooepidemicus.

Determining Acid Phosphatase Presence and Activities

• Through whole cell assays, the study found that these bacteria have two types of acid phosphatase activities, which are most active at pH 5.0 and pH 6.0-6.5.
• Interestingly, only the acid phosphatase active at pH 5.0 was found to be resistant to EDTA, a compound often used in laboratory settings to chelate (bind and remove) metal ions. This resistance is similar to the known resistance of LppC, a lipoprotein acid phosphatase present in a similar species.

Identifying a Cross-Reactive Protein

• The researchers also identified a cross-reactive 32kDa protein which behaved like LppC in both S. equi subsp. equi and S. equi subsp. zooepidemicus. The protein in S. equi subsp. equi was determined to be a surface-accessible lipoprotein, meaning it is present on the cell surface. This finding is important, as these types of proteins can play roles in how bacteria interact with their environment and hosts, potentially influencing infection and disease progression.
• The presence of this cross-reactive protein that behaves like LppC suggests that these two streptococcal sub-species produce a lipoprotein acid phosphatase that is similar to the LppC enzyme found in Streptococcus equisimilis.
• Support for this hypothesis was further strengthened when the researchers found DNA sequences in these bacteria that were similar to the gene coding for LppC in S. equisimilis.