Bacterial cell membrane and associated enzymes

The bacterial cell membrane is a complex phospholipid bilayer that serves as a vital semi-permeable barrier and a scaffold for numerous essential enzymes [1, 8]. It is the site of critical processes including oxidative phosphorylation (via ATP synthase), nutrient transport, and the synthesis of cell wall components like peptidoglycan [1, 4]. Associated enzymes, such as penicillin-binding proteins (PBPs) and transglycosylases, are fundamental for maintaining structural integrity and are the primary targets for beta-lactam antibiotics [2, 6]. Because these structures and enzymes are often distinct from those in eukaryotic cells—for instance, lacking cholesterol and containing unique lipids like cardiolipin—they represent primary targets for various classes of antibiotics [1, 12]. Drugs like polymyxins and daptomycin directly target membrane lipids to cause pore formation and rapid depolarization, while others like bedaquiline inhibit membrane-bound energy metabolism [1, 7]. Targeting this system is a cornerstone of treating bacterial infections, though it faces challenges from emerging antimicrobial resistance and potential off-target toxicity in host tissues [5, 11].

Other names

Bacterial cytoplasmic membraneBacterial inner membraneBacterial cell envelope enzymesBacterial plasma membrane

Drugs targeting the bacterial cell membrane and its associated enzymes act through several distinct mechanisms: (1) direct disruption of the lipid bilayer integrity (e.g., polymyxins, daptomycin), leading to pore formation, ion leakage (potassium efflux), and rapid depolarization [1, 7]; (2) inhibition of membrane-bound enzymes essential for peptidoglycan synthesis, such as penicillin-binding proteins (PBPs) and transglycosylases [2, 6]; (3) inhibition of membrane-associated energy metabolism, such as ATP synthase (e.g., bedaquiline) [1, 3]; and (4) interference with the transport of cell wall precursors across the membrane (e.g., bacitracin) [3, 4].