# Proteomics Analysis in Dairy Products: Cheese, a Review
## 8 Bioactive Peptides
The _Lactobacillus heleticus_ CP790 extracellular protease hydrolyze both \(\alpha\)s1- and \(\beta\)-CN of sour bovine milk resulting in the release of angiotensin converting enzyme (ACE) inhibitory peptides. These peptides exhibited antihypertensive activity in spontaneously hypertensive rats as monitored by systolic blood pressure as many studies indicated [113; 114; 115; 116; 117]. Especially, biological activity analysis revealed great variation among samples of Paramigiano Reggiano with the average ACE-inhibitory and antioxidant activities to be elevated in the LL (low salt-low fat) group compared with the HH (high fat-high salt) group. The differences observed are attributed to factors such as milk quality, somatic cells content and extensive proteolysis by indigenous proteolytic enzymes [118; 119; 120]. Although there are many ways for the presentation of inhibition of ACE, the results of [PERSON] et al. [41] were in accordance with that reported by [PERSON], [PERSON], [PERSON], and [PERSON] [121] for hard and semi-hard cheeses and they were comparable. According to the study [41] the results on DPP-IV-inhibitory activity were lower than those previously reported for the peptide fraction of gouda-type cheese [122], whereas antioxidant activity data were comparable to those already reported in the literature for PR and Cheddar cheeses' peptide fractions [123; 124]. The authors reported for the first time 25 peptides with potential bioactive properties from the total of 40 identified peptides for Paramigiano Reggiano. The remaining 15 peptides were reported in different ripening times [125]. In fact, 13 peptides were ACE inhibitors and already described for their ability to reduce blood pressure in vivo [6]. In more detail, the \(\beta\)-casein-derived peptide KVLPVPQ, isolated from a commercial functional yogurt, demonstrated strong antihypertensive effects in spontaneously hypertensive rats [114, 126]. The peptide LHLPLP, previously found in various cheeses such as Grana Padano, Parmigiano Reggiano, Gorgonzola, and Cheddar, exhibited very low IC50 value against ACE and has been found able to decrease blood pressure in spontaneously hypertensive rats [127, 128, 129, 130]. Additional peptides found in all of the examined PR samples showed potent ACE-inhibitory activity, similar to the peptides NLHLPLPLL, YFPGPIPN, and the peptide YQEPVL [131, 132, 133]. Some other peptides exhibited a high inhibitory effect against ACE and in vivo antihypertensive effect. The S1-casein-derived peptide YKVPQL was detected in the majority of PR samples and has been previously identified as an in vitro and in vivo antihypertensive peptide [129]. Similarly, the \(\beta\)-casein-derived peptide HLPLP has exhibited in vitro and in vivo antihypertensive effect [134]. The lactotrirepeptides VPP and IPP, antihypertensive molecules in vivo in humans, were also found in all PR samples [135]. For the ACE the same standards and peptides have been identified in Parmigiano and Grana [131]. No information is so far available on cheeses, in which antimicrobial peptides occurred after milk proteins' hydrolysis and interaction with cheese microflora [136]. Knowledge of the sequence plays a fundamental role in the studies of food derived bioactive peptides and may help in the identification of the peptide source. Moreover, it can serve as the starting base for the preparation of synthetic analogues to improve the nutritional characteristics of food products. Electrospray ionization tandem mass spectrometry (ESI-MS/MS) was adopted for the identification of bioactive peptides in food matrices using a bioinformatics approach, [137, 138, 139, 140]. An ion trap was used to generate MS/MS and, when required, MS3 spectra, whose potential in solving structural ambiguities in peptide sequences arising from MS/MS measurements/database search has recently been proved to be very successful, leading to the identification of 45 different peptide sequences in fractions of cheese extracts displaying antimicrobial activity [141].