# Legumes as Functional Food for Cardiovascular Disease
## 3 Legumes as Functional Food for Cardiovascular Diseases
### Cardiovascular Benefits of Soybean 7S \(\beta\)-Conglycinin
#### 3.1.2 Soybean Peptides and Their Associated Health Benefits  
Peptides are small protein molecules having between 2 to 21 amino acid residues (<10 kDa), that may exist naturally or be derived from cryptic sequences of native proteins [129; 251; 252] including plants. These peptides may be obtained from different plant sources including various legumes such as soybeans and peas [64; 129]. Originally, these biopeptides are latent but are released through various methods to invoke their biological and/or physiological functions such as their hormone-like activity and influence over various major organ systems [129]. Such methods include hydrolysis via digestion or the proteolytic-enzyme activity of either microbial or plant-origin or from the digestive system [197; 253], from microbial fermentation [254; 255; 256] or during food processing. These peptides offer different health benefits including reduction of blood pressure; anti-hypertensive, hypocholesterolemomic, anti-oxidative, anti-thrombotic, anti-obesity, antiproliferation, anti-cancer, anti-diabetes, immunomodulatory, anxiolytic, and antimicrobial benefits; and the enhancement of mineral absorption and bioavailability [257; 258; 129]. Soybean oligopeptides derived after protease hydrolysis and lactobacilli-fermentation were found to inhibit ACE1, an important enzyme associated with hypertension and CVD [259; 260; 261]. Lactic acid bacteria released ACE inhibitory peptides derived from soybean, soymilk, and soy yoghurt [255]. [PERSON] et al., (2012) [260], detected five novel ACE inhibitory proteins upon protease treatment of hikiwari natto and eight novel ACE inhibitory proteins from protease treated soymilk with the latter having 36-fold ACE-inhibition compared to when untreated soymilk was employed. [PERSON] and [PERSON] (2014) [261] discovered that the LIVTQ pentapeptide that was released via the soybean fermentation with _Lactobacillus casei spp. pseudoplantarum_ and exhibited ACE enzyme inhibition. Using different peptide analogues of this LIVTQ peptide, they found that the glutamine (Q) and threonine (T) residues have an important role towards this ACE enzyme inhibition. ACE1 is a component of the renin-angiotensin-aldosterone system (RAAS) that regulates blood pressure, blood volume, and fluid balance and plays an important role in the physiology of CVD [129]. ACE1 is a non-specific dipeptidyl carboxypeptidase that catalyzes the catabolism of the vasodilator peptide bradykinin, a blood pressure lowering agent belonging to the kallikrenin-kinin system [262; 263; 264]. ACE1 is widely distributed in mammalian tissues as a membrane-bound ectoenzyme in the vascular endothelial cells among others [265]. In RAAS, cleavage of the C-terminus side of the inactive angiotensin I decapeptide results in the active angiotensin II (ACEII) octapeptide. ACEII is also involved in the release of aldosterone from the glomerulosa cells of the adrenal cortex which lowers blood pressure by increasing renal reabsorption of sodium ions and water [266]. Inhibition of ACE is a useful approach to treat hypertension and usually occurs by blocking the first step in RAAS and the negative feedback to angiotensin II [129], thereby, decreasing ACEII production with the corresponding increase of bradykinin levels and decrease in aldosterone secretion [267]. The presence of proline, threonine, glutamine, isoleucine, valine, and leucine in these ACE inhibitory peptides accounted for their ACE-inhibitory properties and most of these peptides were protease-resistant in the gastrointestinal tract [259; 268]. Numerous studies have already claimed the hypocholesterolemocity of the peptides released from the major storage proteins of soybean. Lactostatin (IIAEK) is a pentapeptide derived from bovine \(\beta\)-lactoglobulin. The sequence contains nearly equal amounts of hydrophobic and charged residues with no digestive cleavage sites for reppsin or trypsin [269].