In-silico and in-vitro evaluation of the potential of maize kernels to inhibit trypsin activity

• Maize kernels exhibit in-vitro trypsin inhibitor activity.
• The effect seems to be trypsin-specific and due to bioactive peptides.
• The trypsin inhibition was completely deactivated by heat.
• The extent of in-vitro trypsin inhibitor activity shows a statistically significant positive correlation with the crude protein content of maize kernels.

A study has been conducted in order to evaluate the potential of maize kernels to inhibit trypsin activity in-silico and in-vitro. Assessment of published proteomic data revealed at least one specific trypsin inhibiting peptide within the Zea mays proteome with significant homology to proteins in other grain species but not legumes. Subsequently, a total of 12 maize kernel samples from two countries (Germany and Austria) were screened for their native trypsin inhibitor activity (TIA). The average TIA was 1.27 ± 0.33 mg/g dry matter (DM), ranging between 0.56 and 1.87 mg/g DM, and was no longer detectable after autoclaving (125 °C, 250 kPa, 1 h). Moreover, the degree of inhibition seemed to correlate positively with the crude protein content (r = +0.68*). The trypsin inhibiting effect declined through stepwise addition of exogenous trypsin, highlighting its specific suicidal mode of action. The optimal temperature for denaturation of the inhibitor pool was 82 ± 1 °C. Our results provide, to our knowledge for the first time, information about the trypsin inhibiting potential of maize kernels in-vitro. Furthermore, we identified several significant homologies between a maize bound trypsin inhibitor and peptides which are abundant in the proteomes of other grain species.