Uricase from Alkalihalobacillus clausii, a Candidate for Industrial Application of Reducing Uric Acid Content of Bean Products

Microbial uricase is an essential enzyme in purine degradation and the development of low-purine food. High enzyme activity and an appropriate optimum pH must be established for low-purine food. Uricases from Neurospora crassa, Streptomyces coelicolor, Alkalihalobacillus clausii, Bacillus subtilis, and Brevibacterium casei were heterologously expressed in Escherichia coli. Uricase from Alkalihalobacillus clausii (AC-PUCL) showed the most potent enzyme activity (249.19 IU/mL) at 37 °C and pH 7.0. This is close to the pH of plant-based food. The K_m and K_m/K_cat values of AC-PUCL were 30.12 μM and 1.46 s^-1 μM^-1, respectively. Furthermore, the crystal structures of uricases from different sources revealed that hydrogen bonds could enhance substrate affinity and strong enzyme activity. In addition, the high enzyme activity may be contributed by the active pockets with an appropriate size. Finally, AC-PUCL helped reduce the purine substances in soybean, pea, and kidney bean, with residual uric acid can not be detected at pH 8.6, suggesting a promising industrial application.