Effect of tannic acid on the structure and activity of Kluyveromyces lactis β-galactosidase.

Tannins are compounds with antinutrient properties that hinder food digestibility, prejudicing human and animal nutrition. This work aimed to evaluate the negative effects of tannic acid on Kluyveromyces lactis β-galactosidase catalytic activity and correlate these changes with the protein structure. β-Galactosidase activity decreased in the presence of tannins, which caused changes to the structure of the enzyme, as demonstrated by circular dichroism. It was verified that tannin binds to the protein by a static mechanism. Additionally, isothermal titration calorimetry suggested that tannic acid modified the molecular interaction between β-galactosidase and o-nitrophenyl-β-d-galactoside, reducing their affinity and prejudicing the protein activity. This study helps to understand the effects of tannins on the β-galactosidase structure and how they are related to the enzyme catalytic activity. The alterations in the conformation and activity of the enzyme should be taken into consideration when dairy products are consumed with tannin-rich food.