Final answer:
Pepsin is the enzyme most effective at a pH of 1 or 2, helping in the digestion of proteins in the acidic environment of the stomach.
Step-by-step explanation:
The enzyme most effective at a pH of 1 or 2 is pepsin. This enzyme is secreted in the stomach and is specialized in breaking down proteins into smaller molecules. Its activity is optimal in the highly acidic environment of the stomach, which aligns with a pH of about 1.5. Other enzymes like lingual lipase, maltase, pancreatic amylase, and trypsin do not function optimally at such a low pH. Specifically, trypsin works best in the small intestine with an optimal pH of about 8, helping in the digestion of protein.