What is the substrate name that is abbreviated as pNPP in alkaline phosphatase assays?

What is the substrate name that is abbreviated as pNPP in alkaline phosphatase assays?

• A. Monophosphate
• B. Phenyl phosphate
• C. Disodium phenyl phosphate
• D. Para-nitrophenylphosphate

Answer: (D)

pNPP is para-nitrophenyl phosphate. In alkaline phosphatase assays, the enzyme removes the phosphate group from this substrate, producing para-nitrophenol, which turns yellow under alkaline conditions. This color change is easy to measure spectrophotometrically, typically at 405 nm, making pNPP a convenient chromogenic substrate for detecting phosphatase activity. The other options don’t match the abbreviation: monophosphate is too generic, phenyl phosphate lacks the nitro group, and disodium phenyl phosphate is a salt form that isn’t what pNPP refers to.

pNPP is para-nitrophenyl phosphate. In alkaline phosphatase assays, the enzyme removes the phosphate group from this substrate, producing para-nitrophenol, which turns yellow under alkaline conditions. This color change is easy to measure spectrophotometrically, typically at 405 nm, making pNPP a convenient chromogenic substrate for detecting phosphatase activity. The other options don’t match the abbreviation: monophosphate is too generic, phenyl phosphate lacks the nitro group, and disodium phenyl phosphate is a salt form that isn’t what pNPP refers to.