According to the IFCC recommendations, which substrate is used for determining alkaline phosphatase activity using the Bessey-Lowry-Brock method?

The Bessey-Lowry-Brock method for measuring alkaline phosphatase activity employs para-nitrophenylphosphate as the substrate. This particular substrate is hydrolyzed by alkaline phosphatase to release para-nitrophenol, which can be quantitated colorimetrically. The formation of para-nitrophenol results in a color change that is directly proportional to the enzyme activity, allowing for accurate measurement.

Para-nitrophenylphosphate is favored in this method due to its characteristics, such as the stability of the resulting para-nitrophenol product, which absorbs light at a specific wavelength. This allows for more sensitive detection and quantification compared to other substrates that may not yield equally measurable or stable products.

In summary, para-nitrophenylphosphate is specifically chosen in this method because it provides reliable results for assessing alkaline phosphatase activity, making it the correct answer in this context.