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Phagolysosomes function by reducing the pH of their internal environment. The phagolysosome becomes increasingly acidic through the action of V-ATPase proton pumps, reaching a pH as low as 4.5-5.0. [3] This acidic environment is essential for the activation of hydrolytic enzymes and the denaturation of microbial proteins.
Phagocytosis of a bacterium, showing the formation of phagosome and phagolysosome In cell biology , a phagosome is a vesicle formed around a particle engulfed by a phagocyte via phagocytosis . Professional phagocytes include macrophages , neutrophils , and dendritic cells (DCs).
The phagosome is the organelle formed by phagocytosis of material. It then moves toward the centrosome of the phagocyte and is fused with lysosomes, forming a phagolysosome and leading to degradation. Progressively, the phagolysosome is acidified, activating degradative enzymes. [10] [15] Degradation can be oxygen-dependent or oxygen-independent.
For example, following phagocytosis, the ingested particle (or phagosome) fuses with a lysosome containing hydrolytic enzymes to form a phagolysosome; the pathogens or food particles within the phagosome are then digested by the lysosome's enzymes.
Once a pathogen has been engulfed by a phagocyte, it becomes trapped in an intracellular vesicle called a phagosome, which subsequently fuses with another vesicle called a lysosome to form a phagolysosome. The pathogen is killed by the activity of digestive enzymes or following a respiratory burst that releases free radicals into the phagolysosome.
The two are therefore thought to share similar functions in vivo. [6] However, this makes the determining the precise function of LAMP1 difficult, because while the LAMP1 deficient phenotype is little different than the wild type due to LAMP2 up regulation, [ 6 ] [ 11 ] the LAMP1 / LAMP2 double deficient phenotype leads to embryonic lethality.
NADPH oxidase (nicotinamide adenine dinucleotide phosphate oxidase) is a membrane-bound enzyme complex that faces the extracellular space. It can be found in the plasma membrane as well as in the membranes of phagosomes used by neutrophil white blood cells to engulf microorganisms.
Some bacteria prevent the fusion of a phagosome and lysosome, to form the phagolysosome. [107] Other pathogens, such as Leishmania, create a highly modified vacuole inside the phagocyte, which helps them persist and replicate. [118] Some bacteria are capable of living inside of the phagolysosome.