Structural, evolutionary, and immunogenicity insight into the application of microalgal Spirulina maxima asparaginase in medicinal and industrial purposes

L-asparaginase is an important enzyme that is commonly used for the treatment of Acute Lymphoblastic Leukemia (ALL). The cost-effective characteristics of microalgae make them a favorable source of asparaginase production in both industrial and medical applications. Given the lack of information regarding the algal asparaginase type, its active site, and other structural properties, phylogenetic analyses were conducted to elucidate its classification. The S. maxima asparaginase shares similar ancestry, structural, and catalytic residues with type III asparaginases (Rhizobium etli type). Asparaginase 3D structure was modeled using Alphafold2. The predicted structure demonstrates approximately 100% structural confidence. The binding free energy of asparagine in the enzyme's binding pocket, calculated using docking tools COACH and AutoDock, is estimated to be -4.0 kcal/mol. In contrast to other therapeutically used asparaginases (Escherichia coli and Erwinia chrysanthemi) where threonines play vital roles in catalyzing asparagine, type III asparaginases feature two Ser-Lys tandems responsible for catalyzing the reaction. Furthermore, the phylogenetic distance between therapeutic asparaginases and S. maxima can influence their antigenic properties, leading to variations in their immune responses and antigenic characteristics. Also, through immunogenetic analyses of B- and T-cell epitopes, S. maxima demonstrated different immunogenicity compared to therapeutically used asparaginases. The stable structure, strong binding affinity, and lower immunogenicity properties of S. maxima asparaginase position it as a promising alternative in both the pharmaceutical and food industries.