lumenal side of lysosomal membrane

Definition

Target type: cellularcomponent

The side (leaflet) of the lysosomal membrane that faces the lumen. [GOC:dos]

The luminal side of the lysosomal membrane faces the lumen of the lysosome, a compartment filled with acidic hydrolytic enzymes that are responsible for the degradation of macromolecules. This side of the membrane is characterized by a unique lipid composition compared to other cellular membranes, enriched in phosphoinositides and cholesterol. It also harbors specific transmembrane proteins that play crucial roles in lysosomal function. These proteins include:

- **Lysosomal transmembrane proteins:** These proteins serve as receptors for the delivery of substrates to the lysosome for degradation. They often bind to specific ligands, such as mannose-6-phosphate receptors, which facilitate the transport of newly synthesized lysosomal enzymes from the Golgi apparatus.

- **Proton pumps (V-ATPases):** These pumps actively transport protons into the lysosomal lumen, maintaining its acidic pH, which is essential for the optimal activity of the hydrolytic enzymes.

- **Membrane transporters:** These proteins facilitate the transport of ions, metabolites, and other molecules across the lysosomal membrane, regulating the internal environment of the lysosome and ensuring proper functioning of the degradative processes.

- **Lipid modifying enzymes:** These enzymes contribute to the unique lipid composition of the lysosomal membrane, including the synthesis and degradation of specific phospholipids and cholesterol.

The luminal side of the lysosomal membrane also interacts with the luminal contents, including the degraded products of macromolecules. The membrane itself is resistant to the hydrolytic activity of the lysosomal enzymes, preventing the destruction of the lysosome itself. This stability is crucial for the long-term function of the lysosome and its role in cellular homeostasis.'
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Proteins (2)

Compounds (16)