The Lysosomal Connection..., page-8

The best way to understand the lysosome is that it’s basically the insinkerator of the cell. It’s like a bucket with the interior lined with some very savage enzymes that tear everything apart. It’s the garbage recycling system.

Broken or misfolded proteins and other junk in the cell are recognized by an enzyme (ubiquitinase) which tags them with a small protein called ubiquitin. Anything tagged with ubiquitin is marked as garbage and it gets dragged into the lysosome where it’s shredded like in a blender. The components can then be reused.

And this is why lysosomal disorders are so damaging. The garbage disposal unit doesn’t work and the cell gets gummed up with broken junk and can’t work. That’s what’s going on with MPS, other diseases, and is also a hallmark of aging. The process is so important that the discoverers of the ubiquitination system got the Nobel Prize for Chemistry in 2004.