In 1986, Russo and Moothart (1) published a kinetic experiment for the enzyme lactase using Lact-Aid solution as the source of the enzyme. Lactase is now available in a much more convenient tablet form as Lactaid Fast Act tablets. We have found that using the tablet form gives identical results to those of the solution. One tablet of Lactaid Fast Act is dissolved in 200.0 mL of distilled water and stored at 4 °C. Following the exact procedure of Russo and Moothart, the KM value was 0.9 × 10−3 mol/L (with a Vmax of 0.2 absorbance/min). This value compares nicely with the KM values reported in the Russo and Moothart article (1.7 × 10−3 mol/L) and from the source for the enzyme, Aspergillus oryzae (0.72 × 10−3 mol/L) (2). Specific details regarding assay preparation are available upon request.
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