Abstract: This review systematically summarized the structural characteristics, catalytic mechanisms, expression optimization in heterologous hosts, and progress in molecular engineering of protein glutaminase (PG, EC 3.5.1.44). Derived fromChryseobacterium proteolyticum, PG required proteolytic activation from its zymogen to the mature enzyme for deamidation activity. Heterologous expression systems (e.g.,Escherichia coli,Corynebacterium glutamicum, andBacillus subtilis) have significantly enhanced PG production, withB. subtilisachieving 36.9 U/mL through promoter optimization and fusion tags. Moreover, rational design and computationally aided strategies improved catalytic efficiency and thermostability, such as mutant D1 with a specific activity of 131.6 U/mg and mutant mPG-5M with a 55-fold extended thermal half-life. Despite these advancements, challenges such as endotoxin control in some hosts and high costs of zymogen activation still remain. Future studies should focus on developing safer expression systems and integrating AI-driven enzyme design to promote PG applications in plant-based food industry.

Key words: protein glutaminase, expression optimization, molecular engineering, heterologous expression, plant-based foods