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Comparative Evaluation of Five Proteases for the Production of Multifunctional Bioactive Peptides from Chickpea (Cicer arietinum L.) Protein Isolate: Optimization of Hydrolysis Conditions, Peptide Characterization, and In Vitro Assessment of ACE-Inhibitory, DPP-IV-Inhibitory, and Antioxidant Activities

This study demonstrates that Alcalase-hydrolyzed chickpea protein isolate, particularly its <1 kDa fraction, yields potent multifunctional bioactive peptides with significant ACE-inhibitory, DPP-IV-inhibitory, and antioxidant activities, establishing a comprehensive framework for protease selection and characterization in the development of functional food ingredients.

Original authors: Muhammad Moiz Amir

Published 2026-07-28

📖 6 min read🧠 Deep dive

CC BY 4.0

Original authors: Muhammad Moiz Amir

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine your body as a bustling city where traffic lights and power plants keep everything running smoothly. Sometimes, though, the traffic lights get stuck on "stop," causing a dangerous buildup of pressure (high blood pressure), or the power plants get confused, flooding the streets with sugar (diabetes). For decades, doctors have used synthetic drugs to fix these broken lights and power plants, but these chemical keys can sometimes cause side effects like a persistent cough or stomach trouble. This has sparked a hunt for a gentler, natural alternative hidden right in our kitchens: bioactive peptides. Think of these peptides as tiny, encrypted messages locked inside the proteins of the food we eat, like chickpeas. They are harmless until a specific key—a protease enzyme—unlocks them. Once released, these tiny messengers can float through the body and act like natural traffic controllers, calming the blood pressure and helping manage sugar levels, all while acting as little bodyguards against harmful rust (oxidative stress).

The big question scientists have been asking is: which key is the best at unlocking these messages? While we know enzymes can release these peptides, there hasn't been a clear, head-to-head race to see which one works best for chickpeas, the third most popular legume on the planet. This study steps into the arena to find the ultimate "key" for chickpea protein, testing five different food-grade enzymes to see which one can unlock the most powerful, multi-tasking bioactive peptides.

The Great Enzyme Race

In this study, researchers took chickpea protein isolate (a concentrated protein powder made from desi-type chickpeas, specifically the 'Punjab-2008' variety) and handed it over to five different enzymatic "scissors" to see which one could cut the proteins into the most useful tiny pieces. The contestants were Alcalase, Flavourzyme, papain, trypsin, and Neutrase.

The results were clear: Alcalase was the undisputed champion. While all the enzymes did some cutting, Alcalase chopped the proteins the most thoroughly, achieving a "Degree of Hydrolysis" (a measure of how much the protein was broken down) of 28.4 ± 1.1%. The other enzymes trailed behind, with papain at 22.3 ± 0.9%, Neutrase at 21.5 ± 1.0%, Flavourzyme at 19.7 ± 0.8%, and trypsin at a modest 16.8 ± 0.7%.

But cutting the protein wasn't just about making it smaller; it was about making it useful. The hydrolysate (the soup of tiny peptides) created by Alcalase, which the researchers named CPI-ALC, turned out to be a triple-threat superhero. It showed the strongest ability to:

Block ACE (Angiotensin-I-converting enzyme): A key player in raising blood pressure. The CPI-ALC had an IC₅₀ of 0.34 ± 0.02 mg/mL. (In simple terms, this is the amount needed to stop half the enzyme's activity; a lower number means it's more powerful).
Block DPP-IV (Dipeptidyl peptidase-IV): An enzyme that breaks down insulin-regulating hormones. Its IC₅₀ was 0.82 ± 0.04 mg/mL.
Scavenge free radicals: Acting as an antioxidant. At a concentration of 1 mg/mL, it neutralized 68.5 ± 2.3% of harmful DPPH radicals.

The other enzymes produced hydrolysates that were good, but none matched the all-around power of the Alcalase team.

Finding the Sweet Spot

Once they knew Alcalase was the winner, the researchers didn't just stop there. They wanted to find the perfect recipe to get the most out of it. Using a sophisticated statistical map called Response Surface Methodology (RSM), they tweaked three variables: how much enzyme to use, the temperature, and how long to let it cut.

They discovered the "Golden Zone" for the perfect cut was:

Enzyme amount: 3.2% (weight of enzyme per weight of protein)
Temperature: 52°C
Time: 180 minutes

When they tested this perfect recipe, it worked exactly as predicted, achieving an ACE inhibition of 87.3 ± 1.5%. This confirmed that with the right conditions, you can maximize the production of these helpful peptides.

The Size Matters Rule

The researchers then played a game of "sieve," filtering the Alcalase soup through tiny nets to separate the peptides by size. They found that the smallest pieces were the most powerful. The fraction containing peptides smaller than 1 kDa (which made up 42.3% of the total mass) was the clear winner.

This tiny fraction was a powerhouse:

It blocked 82.6 ± 2.1% of ACE activity.
It blocked 75.4 ± 1.8% of DPP-IV activity.
It scavenged 78.2 ± 2.4% of DPPH radicals.

The larger pieces (over 5 kDa) were much weaker, proving that for these specific health benefits, "smaller is better." The tiny peptides are just the right size to slip into the active pockets of the enzymes they are trying to stop.

The Molecular Detective Work

To understand why these tiny pieces were so effective, the researchers used a high-tech microscope called LC-MS/MS to identify the specific sequences of amino acids in the winning <1 kDa fraction. They found 14 distinct peptide sequences.

They then used computer simulations (molecular docking) to see how these peptides fit into the "locks" of the ACE and DPP-IV enzymes.

For ACE: The peptide VFPLR was the star, with a predicted binding strength of −9.2 kcal/mol. It fit so perfectly it even grabbed onto a zinc ion inside the enzyme, effectively jamming the lock. LAFPG (−8.8 kcal/mol) and RQSHF (−8.5 kcal/mol) were also strong contenders.
For DPP-IV: The peptides SPGAG (−7.6 kcal/mol) and IAPLP (−7.3 kcal/mol) showed the best fits.

The study also looked at how the inhibition worked. It turns out the CPI-ALC mixture acts as a "mixed-type" inhibitor. Imagine a traffic cop who not only stands in front of the car (blocking the active site) but also waves at the driver to slow down from a distance (changing the enzyme's shape). This dual action makes it a very effective blocker.

The Reality Check

While the results are exciting, the authors are careful to keep their feet on the ground. They point out that these tests were done in a lab dish (in vitro), not inside a living body. The "IC₅₀" values, while impressive, are still about 300 times weaker than the synthetic drug captopril. This means these chickpea peptides are not a replacement for emergency medication but rather a potential tool for long-term dietary support.

Furthermore, the study didn't test if these peptides survive the harsh acid of the stomach or if they can actually cross the gut wall to get into the bloodstream. The authors suggest that future research needs to simulate digestion and test these peptides in animals to see if they work in real life. They also note that they only tested one specific variety of chickpea, so other types might behave differently.

The Bottom Line

This study provides the first clear, side-by-side comparison of five enzymes for making bioactive peptides from chickpeas. It confirms that Alcalase, under specific conditions (3.2% enzyme, 52°C, 180 minutes), is the best tool for the job, producing a mix of tiny peptides (mostly under 1 kDa) that can simultaneously target blood pressure, blood sugar, and oxidative stress. While we aren't quite ready to swap our medicine cabinets for chickpea soup just yet, this research lights the path for creating new, natural functional foods that could help keep our internal city traffic flowing smoothly.

Technical Summary: Comparative Evaluation of Five Proteases for the Production of Multifunctional Bioactive Peptides from Chickpea Protein Isolate

Problem Statement
The global burden of non-communicable diseases, specifically hypertension and type 2 diabetes mellitus (T2DM), has driven the search for natural alternatives to synthetic pharmaceuticals like ACE and DPP-IV inhibitors. While bioactive peptides derived from plant proteins offer a promising solution, the literature lacks systematic, head-to-head comparative data to guide the selection of proteases and the optimization of hydrolysis conditions for multifunctional bioactivity. Furthermore, existing studies often evaluate single bioactivities or single proteases, failing to provide an integrated workflow that links peptidomics, molecular docking, and enzyme kinetics to characterize the mechanistic basis of bioactivity in legume-derived hydrolysates.

Methodology
The study utilized chickpea protein isolate (CPI) from the desi-type variety Cicer arietinum L. (Punjab-2008). The experimental design proceeded through five distinct phases:

Comparative Screening: CPI was hydrolyzed under optimal conditions using five food-grade proteases: Alcalase, Flavourzyme, papain, trypsin, and Neutrase. The degree of hydrolysis (DH) and bioactivities (ACE inhibition, DPP-IV inhibition, and antioxidant capacity via DPPH, ABTS, and FRAP assays) were measured for each hydrolysate.
Process Optimization: Based on screening results, Alcalase was selected for further optimization using Response Surface Methodology (RSM) with a Central Composite Design. The variables were enzyme/substrate (E/S) ratio, temperature, and hydrolysis time, with ACE inhibition as the response variable.
Fractionation: The optimized hydrolysate was fractionated via ultrafiltration into four molecular weight ranges (>5 kDa, 3–5 kDa, 1–3 kDa, and <1 kDa) to determine the distribution of bioactivity.
Peptidomics and Docking: The most active fraction (<1 kDa) was analyzed via LC-MS/MS to identify peptide sequences. Identified peptides underwent molecular docking against human ACE (PDB: 1O86) and DPP-IV (PDB: 5J3J) to predict binding affinities and interaction mechanisms.
Kinetic Analysis: The inhibition mechanism of the optimized hydrolysate was determined using Lineweaver-Burk and Dixon plots to calculate inhibition constants ( $K_i$ ) and inhibition types.

Key Results

Protease Performance: Alcalase demonstrated superior performance, yielding the highest degree of hydrolysis (28.4 ± 1.1%) and the most potent bioactivities across all assays. The ranking for bioactivity was consistently Alcalase > Papain > Neutrase > Flavourzyme > Trypsin.
Optimization: RSM identified optimal Alcalase conditions as an E/S ratio of 3.2% (w/w), temperature of 52°C, and hydrolysis time of 180 minutes. These conditions yielded an ACE inhibition of 87.3 ± 1.5%.
Bioactivity Metrics: The unfractionated Alcalase hydrolysate (CPI-ALC) exhibited an ACE inhibition $IC_{50}$ of 0.34 ± 0.02 mg/mL, a DPP-IV inhibition $IC_{50}$ of 0.82 ± 0.04 mg/mL, and significant antioxidant capacity (e.g., 68.5% DPPH scavenging at 1 mg/mL).
Fractionation: The <1 kDa fraction (F4), comprising 42.3% of the total peptide mass, possessed the highest bioactivity, with ACE and DPP-IV $IC_{50}$ values improving to 0.18 ± 0.01 mg/mL and 0.46 ± 0.03 mg/mL, respectively.
Peptide Identification and Docking: LC-MS/MS identified 14 peptide sequences in the <1 kDa fraction, predominantly derived from legumin and vicilin. Molecular docking revealed strong binding affinities for specific sequences:
- ACE: VFPLR (−9.2 kcal/mol), LAFPG (−8.8 kcal/mol), and RQSHF (−8.5 kcal/mol). VFPLR showed interactions with the catalytic Zn²⁺ ion and key active site residues.
- DPP-IV: SPGAG (−7.6 kcal/mol) and IAPLP (−7.3 kcal/mol), both featuring Proline at the P2 position, a key determinant for DPP-IV recognition.
Kinetics: CPI-ALC acted as a mixed-type inhibitor for both ACE ( $K_i$ = 0.18 ± 0.02 mg/mL) and DPP-IV, indicating a combination of competitive and non-competitive inhibition mechanisms.

Significance and Claims
The authors claim this study provides the first standardized comparative dataset for chickpea protein hydrolysis, establishing Alcalase as the most effective protease for generating multifunctional peptides from this substrate. The research advances the field by integrating peptidomics, molecular docking, and enzyme kinetics into a single workflow, offering mechanistic insights into the structure-activity relationships of legume-derived peptides that are rarely found in food peptide literature.

The study highlights the potential of chickpea protein isolate as a source of ingredients for functional foods targeting metabolic syndrome, given the simultaneous presence of ACE-inhibitory, DPP-IV-inhibitory, and antioxidant activities. However, the authors maintain a modest stance regarding clinical applicability. They explicitly note that the in vitro potency of the hydrolysate is approximately 300-fold lower than synthetic pharmaceuticals (e.g., captopril) and emphasize that the findings represent "potential" rather than "therapeutic equivalence." The paper concludes that while the integrated analytical framework is robust, future work must address limitations such as gastrointestinal stability, intestinal transport, and in vivo efficacy before these peptides can be translated into credible functional food ingredients.