Lactose is a disaccharide form of sugar made up of one glucose and one galactose monosaccharide. In animals, millimolar levels of lactose are found in breast milk. In order for lactose to be absorbed into the bloodstream, lactase (secreted from the small intestines) cleaves lactose into glucose and galactose monosaccharides. Some people, particularly infants, lack the enzyme necessary to digest galactose leading to galactose accumulation in blood (Galactosemia) causing enlarged liver, renal failure, cataracts and brain damage

Lactose Assay Kit provides a simple, reproducible, and sensitive tool for measuring lactose concentration in plasma, serum, cell lysates, saliva, urine, and other biological liquid samples. This assay employs a coupled enzymatic reaction system that combines multiple steps. Initially, lactose is converted to galactose and glucose. The glucose is subsequently oxidized, resulting in a colorimetric product which can be measured at 515 nm. The optical density measured at 515 nm is directly proportional to the concentration of lactose present in the sample.

• Microplate reader capable of measuring absorbance at 515 nm
• Precision pipettes to deliver 2 µL to 1 mL volumes
• Tubes to prepare sample dilutions
• 5 mL tubes
• Incubator at 37°C
• Multi-channel pipettes to deliver 20 µL to 200 µL volumes
• MilliQ water or another type of double distilled water (ddH₂O)

1. Add 50 µL of the diluted Lactose standards or samples to the 96-well microtiter plate.
2. Add 10 µL Lactase Reagent to each standard and one half of the paired sample wells, mix thoroughly.
3. Add 10 µL of Hydrolysis Buffer to other half of the paired sample wells. Carefully shake the plate for a few seconds to mix.
4. Incubate the plate for 30 minutes at 37°C with mixing in the dark.
5. Add 50 µL of Glucose Reagent to each well. Incubate the plate at 37°C for 30 minutes with mixing in the dark.
6. Measure the absorbance at 515 nm using a plate reader.