Novel Umami Peptide IPIPATKT with Dual Dipeptidyl Peptidase-IV and Angiotensin I-Converting Enzyme Inhibitory Activities.

A novel umami peptide, IPIPATKT, showed excellent dual dipeptidyl peptidase-IV (DPP-IV) and angiotensin I-converting enzyme (ACE) inhibitory activities, the IC50 values were 64 and 265 µM, respectively. Molecular docking displayed that IPIPATKT was docked into the S1 and S2 pockets of ACE, and it was close to the active site pocket of DPP-IV. The insulin-resistant-HepG2 (IR-HepG2) cell model and human umbilical vein endothelial cell (HUVEC) model showed that the peptide significantly increased the content of glucose, the activities of hexokinase, pyruvate kinase, and the concentration of nitric oxide (p < 0.01), while it reduced the content of endothelin-1 (ET-1). IPIPATKT exhibited a hypotensive effect (-23.5 ± 2.2 mmHg) and attenuated the increase in glucose levels in vivo, as demonstrated using spontaneous hypertensive rats (SHRs) and C57BL/6N mice. We reported the in vivo activities of the umami peptide with dual hypertensive and hypoglycemic effects for the first time.

Isolation, characterization and molecular docking of novel umami and umami-enhancing peptides from Ruditapes philippinarum.

To understand the taste of the Ruditapes philippinarum, 14 novel umami peptides were isolated and identified by gel chromatography, HPLC and UPLC-ESI-QTOF-MS/MS. Separations were combined with sensory evaluations and electronic tongue determinations. The peptide sequences were GRVSNCAA, SEEK, KEMQKN, KSAEN, QIEELEGK, TDVEQEGD, HNESQN, RGEPNND, TGDPEK, KGGGGP, TYLPVH, PAATIPE, GPAGPAGPR and AGAGPTP. All peptides had umami and umami-enhancing qualities, KSAEN and QIEELEGK had higher sensory evaluation than the others, while PAATIPE and HNESQN had the best umami-enhancing taste in a 0.35% MSG solution. Molecular docking of the peptides with T1R1/T1R3 indicated that Ser123, Ser146 and Tyr143 may be important in the interaction of the peptides with T1R3. Arg303, Ser123 and Asp166 appear to be involved in the synergistic effect of umami peptides combined with monosodium glutamate. The omission test and the addition test confirmed that the 14 umami peptides contributed to the umami taste of R. philippinarum.