Lysosomal hydrolases and lysosomal pH machinery

The lysosomal hydrolases and lysosomal pH machinery constitute the primary degradative and metabolic recycling center of the eukaryotic cell. This system comprises over 60 distinct acid hydrolases—including proteases (cathepsins), glycosidases, and lipases—and the vacuolar-type H+-ATPase (V-ATPase) complex, which maintains the acidic luminal environment (pH 4.5–5.0) essential for enzyme activity (Mindell, 2012). These components are critical for the breakdown of macromolecules, cellular homeostasis via autophagy, and the processing of endocytosed materials. Dysregulation of this machinery is the underlying cause of lysosomal storage diseases (LSDs) and is heavily implicated in the pathogenesis of neurodegenerative disorders like Alzheimer’s and Parkinson’s diseases, as well as cancer (Settembre et al., 2013). Therapeutic strategies targeting this system include enzyme replacement therapies (ERTs) to restore deficient hydrolase activity, substrate reduction therapies to decrease the metabolic load, and lysosomotropic agents like hydroxychloroquine that neutralize lysosomal pH to inhibit cancer cell survival or viral entry (Appelqvist et al., 2013). Drugs such as chloroquine and hydroxychloroquine act as lysosomotropic weak bases that accumulate in the lysosome and raise its pH, thereby inhibiting the activity of the resident hydrolases and disrupting cellular processes like autophagy and viral fusion.

Other names

Lysosomal degradative systemLysosomal acidification machineryAcid hydrolasesVacuolar-type H+-ATPase complex

Modulation of lysosomal function through enzyme replacement, substrate reduction, pharmacological chaperoning, or pH neutralization.