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Proceedings of the 31 st European Peptide SymposiumMichal Lebl, Morten Meldal, Knud J. Jensen, Thomas Hoeg-Jensen (Editors)European Peptide Society, 2010Angiotensin I Converting (ACE) Inhibitory Peptides –A Bioinformatic-Assisted Idea of ResearchAnna IwaniakChair of Food Biochemistry, University of Warmia and Mazury, Olsztyn, 10-712, PolandIntroductionAngiotensin I converting enzyme (ACE) inhibitory peptides are known as vasodilators.These peptides are encrypted in many food-derived bioactive proteins and due to theirspecial properties they are found as the valuable food components that can be regarded ashealth-promoting ingredients [1].Much information concerning ACE inhibitory sequences is available in the literatureand computer databases. Specially designed mathematical and statistical algorithms alongwith some bioinformatic and cheminformatic tools are helpful for the understanding thebiological processes which take place in the living organisms [2]. Application of abovementioned tools in defining bioactive peptides in protein is consistent with the idea of foodpeptidomics which covers the research concerning both the composition, changes of thepool of peptides and the methods applied in the studying of these groups of molecules [3].The aim of the work was to elaborate the idea of research of ACE inhibitors (214 diandtripeptides in total) derived from major groups of proteins by means of bio- andcheminformatic tools. To achieve it, the BIOPEP database (http://www.uwm.edu.pl/biochemia) was mostly applied. This strategy involved the use of qualitative andquantitative criteria to evaluate protein as the source of ACE inhibitors as well as theprediction of their release due to the action of digestive enzymes. The prediction ofproducts potentially released by selected endopeptidase(s) was performed by means of oneof the BIOPEP functions called “Enzymes action”.Results and DiscussionThe correlation coefficients illustrating experimental versus theoretical values of activity,were relatively low (e.g. R 2 =0.234 for tripeptides) and their calculation was based on thequantum chemistry descriptors. Thus principal component analysis (PCA) was applied tofind some structural similarities of ACE inhibitors which would decide about their activity.The main characteristic feature in most of the peptides analyzed was the presence of proline(C-end) or aliphatic/aromatic/cyclic amino acid at the N-end (and/or second position intripeptides). Referring the results to the variables affecting the peptides’ bioactivity, thehydrophobicity, the size of a molecule and electronic properties had the influence on theiractivity. The above-mentioned structural similarities between peptides as well asphysicochemical properties of the individual amino acids forming peptides were consistentwith results obtained by other scientific groups [4].The ACE inhibitors possessing the indicated features were used as “standards” to findthem in the protein sequences representing major groups of food. It was enabled by meansof one of the BIOPEP functions i.e. profile of ACE inhibitory activity of a protein. Thisanalysis revealed that milk and plant proteins can be considered as the material forproteolytic processes design. In silico proteolysis specified that β-casein and globulins fromoat and soybean should be qualified for an in vitro experiment. Milk is widely known as thesource of ACE inhibitors and thus was eliminated from the experimental part of theresearch. The oat globulin was firstly taken for the further studies. Some of potentiallyreleased peptides were not defined by BIOPEP as “bioactive”. However, their sequencesrevealed contained three amino acid residue fragments with in vivo confirmed activity (seeBIOPEP database). It covers the idea of fragmentomics, according to which the relativelysmall and active substances are the fragments of larger structures [5].Depending on the enzymes combination used, eighteen peptides could be potentiallyreleased. Experimental verification of results revealed, that oat protein hydrolysates showedthe ACE inhibitory effect. IC 50 values calculated for the hydrolysates of pepsin as well asthe combination of pepsin with trypsin/chymotrypsin were: 0.43, 0.015 and 0.33mg/ml,respectively.Identification of peptides by LC-MS and LC-ESI MS/MS revealed that five out ofeighteen peptides obtained via computer simulation of hydrolysis (BIOPEP) were detected.294