Which substrate is used in the Bowers-McComb method for ALP?

The Bowers-McComb method for measuring alkaline phosphatase (ALP) activity specifically utilizes p-Nitrophenyl phosphate as the substrate. This substrate is hydrolyzed by the enzyme ALP to release p-nitrophenol, which can be quantified colorimetrically. The reaction occurs under alkaline conditions, which is essential for the activity of ALP and the development of the colorimetric product.

The choice of p-nitrophenyl phosphate is particularly advantageous due to its high sensitivity and the distinct color change observed, which allows for accurate measurement of enzyme activity. In contrast, the other substrates listed may not yield the same measurable product or may not be suitable under the reaction conditions optimized for the Bowers-McComb method. Thus, p-Nitrophenyl phosphate is the standard substrate in this assay for ALP activity, making it the correct answer to the question.