Final answer:
The signal that targets enzymes to lysosomes is the mannose-6-phosphate (M6P) tag, which enables their recognition and transport for inclusion in the lysosome where they function in breaking down proteins.
Step-by-step explanation:
The signal on lysosomal enzymes that targets them to lysosomes is a specific oligosaccharide tag, typically mannose-6-phosphate (M6P). These enzymes are synthesized in the endoplasmic reticulum, modified in the Golgi apparatus, and the M6P tag is recognized by M6P receptors. This recognition is crucial for the transport of the enzymes from the Golgi to the lysosomes. Once they reach the lysosomes, these digestive enzymes can carry out their role of breaking down various biomolecules, either from the cell's own components during autophagy or those that are ingested from the outside, such as pathogens in a process called phagocytosis. The lysosomal enzymes are essential for protein turnover, as they degrade intracellular and extracellular proteins into their constituent amino acids.
The signal on lysosomal enzymes that targets them to lysosomes is called the signal peptide. The signal peptide is a short amino acid sequence that is present at the N-terminus of the protein and is recognized by the cellular machinery responsible for sorting and trafficking proteins to their correct destinations. In the case of lysosomal enzymes, the signal peptide directs the proteins to be transported to the endoplasmic reticulum (ER) for further processing and then to the Golgi apparatus, where they are packaged into vesicles that eventually fuse with lysosomes.