**10. Cyclo(his-pro)**

Cyclo(His-Pro),(CHP),a naturally occurring, cyclic dipeptide structurally related to thyrotro‐ pin-releasing hormone, was obtained from soybean meal by hydrolysis with flavourzyme and alcalase. When rat insulinoma cells (RINm5F) were exposed to 2 mM streptozotocin (STZ), insulin secretion declined to approximately half. CHP treatment restored the insulinsecreting activity of RINm5F cells to approximately 71% of that of untreated control cells. CHP significantly protected the cells from STZ -mediated cytotoxicity via reduction of STZinduced nitric oxide production (2.3-fold) and lipid peroxidation (1.9-fold). STZ-induced apoptotic events, including activation of caspase-3, poly(ADP-ribose) polymerase (PARP) cleavage, and DNA fragmentation in RINm5F cells were attenuated by CHP. These results suggest that CHP could be employed as a protective and therapeutic agent against STZmediated cytotoxicity and apoptosis [13].

### **11. Immunostimulating glutamine-rich peptide**

An immunostimulating glutamine-rich peptide, isolated from the soybean protein fraction digested with *Rhizopus oryzae* Peptidase R, was located at or in the vicinity of the glutaminerich region 202 to 222 of the glycinin G4 subunit. The peptide significantly upregulated the number of CD8(+), CD11b(+), and CD49b(+) cells in C3H/HeN mouse spleen cell cultures. Two chemically synthesized glutamine-rich peptides (QQQQQQKSHGGR and

KQGQHQQEEEEE), corresponding to residues 202 to 213 and residues 214 to 225 of the gly‐ cinin G4 subunit, elevated the number of interleukin (IL)-12(+)CD11b(+) cells. Peptide 202-213 increased the number of CD49b(+), IL-2(+)CD4(+), and interferon-gamma(+)CD4(+) cells, and stimulated the cytotoxic activity of splenocytes toward K562 human erythroleuke‐ mia cells. The data suggest that the glutamine-rich region of the soybean glycinin G4 subu‐ nit enhances the cellular immune system in murine splenocyte cultures [14].
