Improving Water Solubility of Docosahexaenoic Acid with Chickpea Protein Isolates Deamidated by Protein-glutaminase

In this study, we investigated the effects of protein-glutaminase (PG) modification on the physicochemical and techno-functional properties of chickpea protein isolates (CPI). The deamidated chickpea protein isolates (DCPI) were used as carriers for docosahexaenoic acid (DHA). Treatment with PG led to deamidation of the CPI, resulting in increased water solubility, surface hydrophobicity, and reduced particle size. Adding CPI modified by 5 U/g PG for 8 h (CPI-8 h) significantly decreased the turbidity of DHA in aqueous solution. Fluorescence spectroscopy showed that CPI-8 h had a higher binding constant with DHA compared to the original CPI, increasing from 3.2 × 10³ M^–1 to 3.9 × 10³ M^–1. Thermodynamic analysis revealed that the binding of both CPI-0 h and CPI-8 h with DHA was a spontaneous, endothermic, and entropically driven process, emphasizing the hydrophobic nature of the interaction. Deep learning tools were used to simulate the structure of the major protein component in CPI-0 h and CPI-8 h, with CPI-8 h showing a higher propensity to bind with DHA in molecular docking simulations. These findings highlight the potential of PG-modified CPI as an effective carrier for DHA.