In general, ACE-inhibitory peptides that have been found to have antihypertensive activity in SHR have IC50 values lower than 150 uM. However, in some cases extent of ACE inhibitory activity of the peptide is not correlated with the antihypertensive activity.92 Some peptides show strong antihypertensive activity at a low dose even though the possess a low ACE inhibitory activity.30 For example Tyr-Pro Pro found in B-CN, K-CN, and aSI-casein, purified from a yogurt-like product fermented by Lb. helveticus, showed a significant antihypertensive activity after oral administration to SHR, even though it has a very low ACE inhibitory activity(IC50 of 720 M).93.94 The antihypertensive activity of Tyr-Pro was measured by observing a drop of the systolic blood pressure in SHR after oral administration. Although Tyr-Pro has a strong antihypertensive activity, it has a low inhibitory activity against ACE, suggesting another possible way of controlling hypertension. Chymase, a major angiotensin-II forming enzyme, plays a role in the development of hypertension in the vessels of the heart.95 the Tyr-Pro peptide could have an inhibitory effect on that enzyme. In addition, antihypertensive peptides also display an effect on bradykinin levels by inhibition of,ACE.69 Further digestion of the precursors of the bioactive peptides themselves by digestive enzymes could affect the activity of the peptides by enhancing or inactivating their physiological activity. The liberation of C-terminal amino acid residues of the peptide B-casein f169-175 afther in vitro pancreatin digestion increases tremendously the ACE-inhibitory activity and consequently the antihypertensive effect in vivo.30 It has been demonstrated that