Endopeptidaseja

Endopeptidaseja is a proteolytic enzyme that belongs to the serine peptidase family and is predominantly found in certain Gram‑negative bacteria. The enzyme is encoded by the *epja* gene and is often expressed in response to nutrient limitation or during the transition to stationary phase. Endopeptidaseja catalyzes the hydrolysis of internal peptide bonds, preferentially targeting bonds adjacent to alanine or valine residues, and is thought to play a role in remodeling the bacterial cell wall and regulating the retention of peptidoglycan fragments.

The protein typically contains a classical catalytic triad (Ser, His, Asp) in a conserved β‑lactamase like fold, and its activity is dependent on metal ion cofactors such as Ca²⁺ or Mn²⁺. In vitro assays using synthetic peptide substrates have revealed a Km in the micromolar range and a k_cat of approximately 10 s⁻¹ under optimal conditions. Endopeptidaseja is secreted via a Sec-dependent pathway and localizes to the periplasmic space where it interacts with other cell‑wall‑associated proteins.

Physiologically, Endopeptidaseja contributes to the turnover of peptidoglycan fragments, thereby influencing bacterial shape, resistance to osmotic stress, and immune evasion. It has been studied as a potential target for novel antimicrobial agents because its inhibition can lead to accumulation of toxic peptidoglycan intermediates. Additionally, some research has suggested a role for Endopeptidaseja in bacterial virulence regulation, wherein its expression is modulated during host infection.

In summary, Endopeptidaseja is a periplasmic serine protease with a specialized substrate profile that participates in peptidoglycan metabolism and is an emerging point of interest in antimicrobial research.