Quantification of Reducing Sugars Using the BCA Protein Assay

The BCA (bicinchoninic acid) assay is usually used to quantify proteins, but it can also be used to measure reducing sugars. For a range of sugars the response is linearly related to the amount of sugar in the reaction. Although the final absorbance and end points are the same, an examination of the effect of time and temperature show that each sugar reacts at a different rate, even though they all start and end at the same points. From this rate data, we have determined a temperature coefficient for the reaction of several types of reducing sugars. The reactions have multiple steps and the temperature coefficient is related to the activation energy for the combination of steps. This BCA assay for reducing sugars can be used for many other purposes as well, such as the invertase enzyme activity, acid catalyzed hydrolysis of sucrose and starch, and to quantify the sugars in soft drinks.