# Characterization of Guanine Deaminase from Kluyveromyces marxianus and Its Industrial Application to Reduce Guanine Content in Beer

## TL;DR

This paper identifies a highly active guanine deaminase from Kluyveromyces marxianus that effectively reduces guanine in beer, making it suitable for low-purine food production.

## Contribution

The study introduces a novel, high-activity guanine deaminase from Kluyveromyces marxianus with optimal conditions and industrial potential.

## Key findings

- KM-GDA exhibited the highest enzyme activity (2.21 IU/mL) at 30°C and pH 6.5.
- Crystal structure analysis showed hydrogen bonds and active pocket size enhance enzyme activity.
- KM-GDA reduced guanine by 80.33% in beer wort and 80.00% in matured beer.

## Abstract

Guanine deaminase (GDA) catalyzes the first step in purine catabolism by converting guanine to xanthine. Despite its significant role in the development of low-purine food, studies on GDA remain limited compared to other metabolic deaminases. To identify a GDA with high enzyme activity and appropriate optimum parameters, GDAs from Kluyveromyces lactis, Kluyveromyces marxianus, Lentilactobacillus kefiri, and Lactobacillus buchneri were heterologously expressed in Escherichia coli. The GDA from Kluyveromyces marxianus (KM-GD) showed the most potent enzyme activity (2.21 IU/mL) at 30 °C and pH 6.5, which is close to the pH of saccharified wort. Furthermore, analyzing the crystal structures of GDAs from different sources revealed that hydrogen bonds could enhance substrate affinity and strengthen enzyme activity. In addition, active pockets with an appropriate size may contribute to high enzyme activity. Finally, KM-GD helped reduce guanine by 80.33% in beer wort and by 80.00% in matured beer, thus suggesting its promise for industrial application in low-purine food production.