8-Quinolyl phosphate as a substrate for the fluorimetric determination of alkaline phosphatase

Background: Alkaline phosphatase (ALP) is an important target for clinical analysis. 8-Quinolyl phosphate (QP) was developed as a new substrate for the fluorimetric determination of ALP activity. Methods: QP is a strong fluorescent substance and the product of the enzyme reaction is 8-bydroxyquinoline (HQ), which has no fluorescence. Under the optimal conditions for the determination of ALP, the decreased fluorescence intensity via the enzyme reaction is proportional to ALP activity. The fluorescence intensity was measured at gimel ex/gimel em=318/495 nm before and after the enzyme reaction. Results: QP reacted with ALP in the buffer solution of PH = 9.5 and incubated for 20 min at 37.0 degrees C were selected as the optimal conditions for the determination of ALP. The linear range and detection limit for the determination of ALP are 1.0-16.0 and 0.229 U/l, respectively. With this method, ALP could be applied to assess ALP in human serum and the results were evaluated by comparison with a standard colorimetric assay using p-nitrophenyl phosphate as ALP substrate. Conclusions: This method is simple, practical and can be used as an alternative to assess ALP in clinical analysis. (c) 2006 Elsevier B.V. All rights reserved.