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Biochemistry

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Analyzing Enzyme Assay Results

BIOCHM-RAD3J6

Lactate dehydrogenase is an enzyme that catalyzes the reaction shown. The substrate, NADH, absorbs at 340 nm and none of the other molecules in this reaction do. Consequently, this enzyme can be assayed by mixing the enzyme with its substrates pyruvate and NADH and measuring the decrease in absorbance at 340 nm.

$$\text{pyruvate + NADH} \ \xrightarrow [ ]{ } \ \text{lactate + NAD}$$

A student attempted to do the enzyme assay three times. One time, the assay was done correctly but the other times, mistakes were made. In one trial, the student omitted the NADH from the enzyme assay and in another, the student mistakenly boiled the enzyme prior to the assay.

While doing the assay, the absorbance was measured at 340 nm over time and the results are shown in the table.

contains the results for the enzyme assay being done properly and

contains the results from the trial were the NADH was not added.

The results of the trial in which the enzyme was boiled prior to use is

. The results are shown in the table.