Why does lactate dehydrogenase dependence matter for target validation?

The assay relies on exogenous lactate dehydrogenase to convert lactate to pyruvate, ensuring that signal generation is not confounded by endogenous enzymes in the lysate. This dependence allows specific attribution of colorimetric signal to lactate concentration, supporting accurate target validation in metabolic pathways.

How does isolating lactate as the independent variable fit the discovery pipeline?

By quantifying lactate levels as a function of experimental conditions, the assay isolates lactate as a measurable output of glycolytic flux, enabling researchers to link genetic or pharmacological perturbations to changes in energy metabolism. This supports early discovery by providing a de-risked, quantitative biomarker of pathway activity.

What do quantitative absorbance measurements at 570 nm enable?

Absorbance readings at 570 nm, after background subtraction, are used to generate a standard curve from known lactate concentrations, allowing interpolation of lactate levels in test samples. This quantitative output enables dose-response analysis and comparison across experimental groups in screening campaigns.

Why do duplicate analysis requirements matter for cross-functional collaboration?

Performing duplicate measurements for each sample increases data reliability and reduces technical variance, which is essential for consistent interpretation across biology, screening, and analytics teams. This practice supports reproducible handoffs between discovery and preclinical units.

What statistical analysis capabilities are required before implementation?

Teams must be able to generate a calibration curve, perform linear regression, and interpolate unknown concentrations from the curve, followed by dilution factor correction (e.g., multiplying by 2.25 as noted in the protocol). These capabilities ensure accurate lactate quantification from raw absorbance data.

Colorimetric Assay for Quantification of Lactate in Test Samples

JoVE Encyclopedia of Experiments

Biological Techniques

0 views • 3:08 min • July 8th, 2025

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In living cells, under anaerobic conditions, the enzyme lactate dehydrogenase converts pyruvate — an end product of glycolysis — to lactate — a key metabolite. The amount of lactate produced in the cells reflects their metabolic status.

To quantify the intracellular lactate concentration, begin with a test sample of protein-free, nematode cell lysate. Supplement other wells of a multi-well plate with a lactate solution of various known concentrations.

The lysate lacks all proteinaceous enzymes, including endogenous lactate dehydrogenase, ensuring accurate lactate quantification.

Add a lactate assay buffer into each well to maintain the appropriate pH for optimum enzymatic activity. Supplement the wells with a reaction mix containing the lactate dehydrogenase enzyme, nicotinamide-adenine dinucleotide — NAD — a coenzyme, and a colorimetric probe and incubate.

During incubation, lactate dehydrogenase catalyzes the oxidation of cellular lactate to pyruvate, with a simultaneous reduction of NAD into NADH. The generated NADH reacts with the colorimetric probe to produce a purple product.

Spectroscopically measure the purple solution's absorbance for the test sample and lactate standards at 570 nanometers. Plot the absorbance values of the lactate standards and generate the calibration curve.

Finally, compare the absorbance value of the sample with the lactate standards to determine the amount of lactate present in the test sample.

To measure the concentration of lactate, use a colorimetric assay kit to carry out duplicate analysis for the test samples. Add 10 microliters of the test samples to each well of a 96-well plate, and then add lactate assay buffer to each sample to adjust the volume to 50 microliters.

Dilute 100 millimolar L(+)-Lactate standard with lactate assay buffer to 1 millimolar. Then, into a series of wells, add 0, 2, 4, 6, 8, and 10 microliters of diluted L(+)-Lactate standard. Add 50 microliters of reaction mix into each well, and incubate at room temperature protected from light for at least 30 minutes for the color to develop.

Finally, use a microplate reader to measure the absorbance of each well at 570 nanometers. Subtract the absorbance of the background control mix from the absorbance of the reaction mix. Then, plot the lactate standard curve, and calculate the lactate concentrations from the curve by multiplying each concentration by 2.25.