Question

What acts as an address directing lysosomal enzymes to lysosomes?

1) a lysosomal peptide
2) mannose-6-sulfate residues on the enzyme
3) mannose-6-phosphate residues on the enzyme
4) a signal peptide on the enzyme
5) a stroma transfer peptide on the enzyme

Answer 1

Lysosomal enzymes are tagged with mannose-6-phosphate residues that direct them to lysosomes, where they degrade biomolecules. The tagging occurs in the endoplasmic reticulum and is recognized by receptors in the Golgi apparatus.

Step-by-step explanation:

In the cell, lysosomal enzymes are specifically tagged to ensure they reach the correct destination, which is the lysosome. This tagging involves a mannose-6-phosphate (M6P) residue which is recognized by M6P receptors in the Golgi apparatus. The enzymes are initially synthesized in the rough endoplasmic reticulum (ER) where they undergo post-translational modification, including the addition of the critical M6P marker.

The proteins are then transported to the Golgi apparatus for further processing. Inside the Golgi, the presence of the M6P tag directs the enzymes to be packaged into vesicles that will eventually become lysosomes. Upon leaving the Golgi, the vesicles with M6P-tagged enzymes will specifically fuse with lysosomes, delivering the enzymes to their correct location where they can perform their function of degrading biomolecules.