Which substrate is associated with the King-Armstrong method for alkaline phosphatase measurement?

• A. p-nitrophenylphosphate
• B. Phenylphosphate
• C. Alpha-naphthyl phosphate
• D. Beta-glycerophosphate

Answer: (B)

The substrate used in the King-Armstrong method is phenyl phosphate. In this assay, alkaline phosphatase acts on phenyl phosphate to release phenol, and that phenol is then detected through a color-forming reaction that can be measured photometrically. This approach relies on the generation of phenol from the substrate, distinguishing it from other alkaline phosphatase methods that use substrates like p-nitrophenyl phosphate, alpha-naphthyl phosphate, or beta-glycerophosphate, which produce different chromogenic products. Therefore, phenylphosphate is the substrate associated with the King-Armstrong method.