Where do most lysosomal enzymes originate?

Most lysosomal enzymes are synthesized in the rough endoplasmic reticulum (ER) and then undergo modifications in the Golgi apparatus. This process is crucial for their proper functioning.

Initially, these enzymes are translated as inactive precursors known as preproenzymes. Once synthesized in the rough ER, they are then transported to the Golgi apparatus, where they undergo specific post-translational modifications, such as the addition of mannose-6-phosphate. This modification is critical because it serves as a sorting signal that directs the enzymes to lysosomes.

After being properly processed and tagged in the Golgi, they are packaged into vesicles that deliver them to lysosomes, where they become active and help in the breakdown of macromolecules. This well-coordinated pathway ensures that lysosomal enzymes are correctly folded, modified, and sorted for their vital role in cellular degradation processes.