From Teosinte to Modern Maize: Unveiling the Hidden Loss of Bioactive Proteins

Introduction 
Over centuries, selective breeding has transformed a wild grass, teosinte, into modern maize (Zea mays), increasing its yield at the cost of health-beneficial compounds like storage-protein-derived peptides. Although genotypic changes due to domestication are well-studied, the associated phenotypic changes, particularly in protein composition and bioactive properties, remain underexplored. 

Objective 
To investigate changes in the quality and quantity of maize proteins due to domestication and evaluate the antioxidant and anti-inflammatory properties of peptides derived from these proteins. 

Methodology 
This study included 26 modern maize (MM) varieties, 25 landrace (L) varieties, and 25 teosinte (T) varieties. Protein content in maize kernels was quantified, followed by simulated gastrointestinal (GI) digestion. The digesta from all varieties were analyzed for peptide content, degree of hydrolysis, and peptide composition. Finally, the bioactive properties of the digesta were assessed using in-vitro HT-29 cell assays. 

Results and Discussion 

The results revealed that teosinte kernels contained three times the average protein content of modern maize and landraces, suggesting that domestication prioritized starch accumulation at the expense of protein. Despite this, proteins in modern maize and landraces exhibited a higher degree of hydrolysis during simulated gastrointestinal digestion, resulting in comparable peptide content across all groups. Peptide profiling showed that digested teosinte kernels were richer in dipeptides and tripeptides containing hydrophobic residues. UniDL4BioPep, a deep-learning-based predictive language modeling tool, estimated that many of the peptides identified in digested teosinte kernels possess antioxidative properties. Further, bioactivity assessments demonstrated that teosinte digesta significantly reduced oxidative stress in HT-29 cells and lowered the expression of the pro-inflammatory marker IL-8 compared to modern maize and landraces.

Conclusion 
The findings suggest that successive breeding has reduced the abundance of bioactive peptides in modern maize, which were present in teosinte. The peptides, particularly those with antioxidant and anti-inflammatory properties, may offer potential health benefits.