Structure-function properties of flaxseed protein-derived multifunctional peptides

dc.contributor.authorUdenigwe, Chibuike Chinedu
dc.contributor.examiningcommitteeMoghadasian, Mohammed (Human Nutritional Sciences) O, Karmin (Animal Science and Physiology) Wanasundara, Janitha (Agriculture and Agri-Food Canada)en
dc.contributor.supervisorAluko, Rotimi (Human Nutritional Sciences)en Nutritional Sciencesen_US of Philosophy (Ph.D.)en_US
dc.description.abstractFood protein-derived peptides have increasingly become important sources of ingredients for the formulation of therapeutic products. The main aim of this work was to study the in vitro and in vivo bioactive properties of structurally diverse group of peptides produced through enzymatic hydrolysis of flaxseed proteins (FP). Hydrolysis of FP with seven proteases followed by fractionation into low-molecular-weight (LMW) cationic fractions yielded multifunctional peptides that inhibited angiotensin converting enzyme (ACE) and renin activities, which are molecular targets for antihypertensive agents. The LMW peptides also exhibited antioxidant properties by scavenging free radicals and inhibiting amine oxidase activity. The peptide fractions showed inhibition of calmodulin-dependent phosphodiesterase, an enzyme that has been implicated in the pathogenesis of several chronic diseases. Moreover, FP hydrolysis with thermolysin and pronase followed by mixing with activated carbon yielded branched-chain amino acids (BCAA)-enriched multifunctional peptide mixture (Fischer ratio of 23.65) with antioxidant properties and in vitro ACE inhibition; Fischer ratio of 20.0 is considered minimum for therapeutic purposes. The BCAA-enriched peptide product can be used in clinical nutrition to treat muscle wasting symptoms associated with hepatic diseases. Furthermore, an arginine-rich peptide mixture (31% arginine versus 11% in the original flaxseed protein) was produced by hydrolysis of FP with trypsin and pronase followed by separation using electrodialysis-ultrafiltration. Arginine plays important physiological roles especially as precursor to vasodilator, nitric oxide. The arginine-rich peptide mixture exhibited in vitro ACE and renin inhibition and led to decreased systolic blood pressure (–17.9 and –11.7 mmHg, respectively at 2 and 4 h) after oral administration to spontaneously hypertensive rats. For the first time in the literature, we showed that arginine peptides have superior physiological effects when compared to the amino acid form of arginine. Lastly, quantitative structure-activity relationship studies using partial least squares (PLS) regression yielded two predictive models for renin-inhibiting dipeptides with z-scales amino acid descriptors. The PLS models indicated that hydrophobic and bulky side chain-containing amino acids contribute to renin inhibition if present at the amino- and carboxyl-terminal of dipeptides, respectively. Based on this study, Ile-Trp was discovered as potent renin-inhibiting dipeptide, and may serve as a useful template for the development of potent antihypertensive peptidomimetics.en
dc.description.noteFebruary 2011en
dc.format.extent1905223 bytes
dc.identifier.citationUdenigwe CC, Aluko RE (2010). Antioxidant and angiotensin converting enzyme-inhibitory properties of a flaxseed protein-derived high Fischer ratio peptide mixture, Journal of Agricultural and Food Chemistry 58:4762-4768en
dc.identifier.citationUdenigwe CC, Lu Y-L, Han C-H, Hou W-C, Aluko RE (2009). Flaxseed protein-derived peptide fractions: Antioxidant properties and inhibition of lipopolysaccharide-induced nitric oxide production in murine macrophages, Food Chemistry 116:277-284en
dc.identifier.citationUdenigwe CC, Lin Y-S, Hou W-C, Aluko RE (2009). Kinetics of the inhibition of renin and angiotensin I-converting enzyme by flaxseed protein hydrolysate fractions, Journal of Functional Foods 1:199-207en
dc.rightsopen accessen_US
dc.subjectFlaxseed proteinen
dc.subjectBioactive peptidesen
dc.subjectStructure-function studiesen
dc.subjectEnzymatic hydrolysisen
dc.titleStructure-function properties of flaxseed protein-derived multifunctional peptidesen
dc.typedoctoral thesisen_US
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