Photometric determination of enzyme activity

Progress curves are usually not established in solid-phase EIA instead, end-point transformation of S - P is measured after a standard time and plotted against standard curves. From the Lambert-Beer law  

The specific activity of the enzyme, i.e. activity per mg (Ce = concentration of enzyme in mg/ml), is then  

Since specific enzyme activity relates to mole of substrate produced per mg of enzyme, it should be multiplied by a factor 10 x MW (enzyme)/10 to obtain the TN (if enzyme is not multimeric). 

No enzyme fulfills all the criteria for an ideal label in EIA (Table 10.1) and a compromise has to be made. 

In solid-phase EIA, the influence the solid phase has on the enzyme (Section 9.2.2) should be minimal. Conjugation should be easy and the conjugates should be active and stable. These are undoubtedly major factors for the frequency of the selection of horseradish peroxidase (POase) or P-galactosidase (BGase). Alkaline phosphatase (AP-ase), which is difficult to conjugate in defined form (extensive polym- 

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Koller, E. Wolfbeis, O. S. Preparation of pyrenesulfonic acid derivatives for photometric determination of enzyme activity. AT 385755,1988. 

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