Various peptides having ACE inhibition activity in vitro have been isolated from different proteins including asi- and B-casein(CN) ;74.81 whey proteins;82,83 soy proteins;84 gelatin, fish proteins, and maize;85 and gluten, zein, and hordein,86 but milk proteins are the principal sources for such bioactive peptides(Table 7.4).
Different kinds of fermented milk have shown a high hemodynamic regulatory activity. Antihypertensive peptides derived from fermented milk have been studied in vivo.87 LAB have extracellular proteinases that hydrolyze casein to release ACE inhibitory peptides.88 Some antihypertensive peptides are released from casein by a purified extracellular proteinase from Lb. helveticus CP790(Table 7.4).31 Moreover, a dodecapeptide derived from casein enzymatic hydrolysate has been found to have antihypertensive properties in vivo.89 Two other antihypertensive peptides, Val-Pro-Pro and Ile-Pro-Pro, were purified from a sour milk called Calpis fermented with Lb. helveticus and Saccharomyces cerevisiae.90 Their amino acid sequences can be found at three positions in bovine caseins B-CN(f74-76), B-CN(f84-86) and K-CN(fi08-110). As shown in Table 7.4, these peptides have a low IC50 and therefore a strong ACE inhibitory activity.