The substrate shown below was discovered to be held by some amino acid side chains in an enzyme's active site. Can the amino acids phenylalanine, valine, and lysine be found in the active site? Why?

• A. Yes, phenylalanine and valine can form a hydrophobic interaction with the benzene ring of the substrate, while lysine can form an ionic interaction with the carboxylate ion of the substrate.
• B. No, phenylalanine and valine can form a hydrophobic interaction with the benzene ring of the substrate, while lysine's positively charged side chain is not likely to interact with the substrate's benzene ring.
• C. Yes, phenylalanine and valine can form a hydrophobic interaction with the benzene ring of the substrate, while lysine's charge is neutralized in the active site, allowing it to interact with the substrate.
• D. No, because phenylalanine and valine are too bulky to fit in the active site with the substrate, and lysine's positively charged side chain is not likely to interact with the substrate's benzene ring.

Answer: (A)