Vacuolelysosome

Vacuolelysosome is a term used in some discussions of cell biology to describe a compartment that blends features of a vacuole and a lysosome. In this conceptual view, vacuolelysosomes are membrane-bound organelles or functional units within the endomembrane system that combine storage with degradative capabilities.

Biogenesis and structure: Vacuolelysosomes are envisioned to originate from maturation and fusion events among endosomes, autophagosomes, and vacuolar precursors, acquiring hydrolytic enzymes and an acidic lumen through trafficking routes involving the Golgi apparatus. They may vary widely in size and composition between organisms and cell types.

Biochemical properties: They can harbor lysosomal hydrolases, proteases, and acid phosphatases, and maintain an acidic pH via proton pumps such as V-ATPases. Marker proteins associated with both lysosomes and plant lytic vacuoles have been reported in models exploring vacuole-lysosome continuum.

Functions: In this framework, vacuolelysosomes would participate in degradation of endocytosed material and worn organelles, autophagic recycling, and storage of metabolites, ions, and osmolytes. They would intersect with endocytic and autophagic pathways and may contribute to cellular homeostasis under stress.

Taxonomic status: The vacuolelysosome concept is not a widely adopted category in standard textbooks. It is mainly used in theoretical discussions, comparative cell biology, or as a way of describing the functional continuum between storage vacuoles and degradative lysosomes.

See also: lysosome; vacuole; lytic vacuole; endolysosomal system; autophagy.