H-Gly-D-Tyr-OH

A cyclic pentapeptide c(Tyr-Leu-Ala-Gly-Pro) (I), which was isolated and identified from Pseudostellaria heterophylla medicinal herbs, and two cyclic heptapeptides, c(Gly-Tyr-Gly-Gly-Pro-Phe-Pro) (II) and c(Gly-Ile-Pro-Tyr-Ile-Ala-Ala) (III), which were isolated and identified from Stellaria yunnanensis Franch (M), were synthesized by using 3-(diethoxyphosphoryloxy)-1,2,3-benzotriazin-4(3 H)-one (DEPBT) as a coupling reagent in solution, and mediated by different metal ions, from their linear peptide precursors H-Tyr-Leu-Ala-Gly-Pro-OH (I-1) and H-Ala-Gly-Pro-Tyr-Leu-OH (I-2), H-Gly-Tyr-Gly-Gly-Pro-Phe-Pro-OH (II-1) and H-Gly-Ile-Pro-Tyr-Ile-Ala-Ala-OH (III-1), respectively. The results show that alkali metal ions can improve the cyclization yields and/or the cyclization rates of linear peptide precursors, such as Na(+) ion is favorable for the cyclization of linear pentapeptides and Cs(+) ion is favorable for the cyclization of linear heptapeptides, while some bivalent and trivalent metal ions, such as Mg(2+), Ca(2+), Zn(2+), Fe(2+), Ni(2+) and Cr(3+) reduced/inhibited both the cyclization yields and the cyclization rates of the linear peptide precursors. The circular dichroism spectra of I-1, II-1 and III-1 with different metal ions were studied to elucidate the changes in their secondary structures. It is shown that Cs(+) can induce and stabilize the type I beta-turn conformation in the linear heptapeptide II-1 and the type II beta-turn conformation in the linear heptapeptide III-1.

Highly purified preparations of thymidylate synthase, isolated from calf thymus, and L1210 parental and FdUrd-resistant cells, were found to be nitrated, as indicated by a specific reaction with anti-nitro-tyrosine antibodies, suggesting this modification to appear endogenously in normal and tumor tissues. Each human, mouse and Ceanorhabditis elegans recombinant TS preparation, incubated in vitro in the presence of NaHCO(3), NaNO(2) and H(2)O(2) at pH 7.5, underwent tyrosine nitration, leading to a V(max)(app) 2-fold lower following nitration of 1 (with human or C. elegans TS) or 2 (with mouse TS) tyrosine residues per monomer. Enzyme interactions with dUMP, meTHF or 5-fluoro-dUMP were not distinctly influenced. Nitration under the same conditions of model tripeptides of a general formula H(2)N-Gly-X-Gly-COOH (X = Phe, Tyr, Trp, Lys, Arg, His, Ser, Thr, Cys, Gly), monitored by NMR spectroscopy, showed formation of nitro-species only for H-Gly-Tyr-Gly-OH and H-Gly-Phe-Gly-OH peptides, the chemical shifts for nitrated H-Gly-Tyr-Gly-OH peptide being in a very good agreement with the strongest peak found in (15)N-(1)H HMBC spectrum of nitrated protein. MS analysis of nitrated human and C. elegans proteins revealed several thymidylate synthase-derived peptides containing nitro-tyrosine (at positions 33, 65, 135, 213, 230, 258 and 301 in the human enzyme) and oxidized cysteine (human protein Cys(210), with catalytically critical Cys(195) remaining apparently unmodified) residues.

Sheep fasciolosis is a devastating burden for the livestock industry. We herein report on immunodiagnosis of fasciolosis, and significant protection of sheep against challenge infection with Fasciola gigantica following immunization with a peptide based on the H-Asp(110)-Lys-Ile-Asp-Trp-Arg-Glu-Ser-Gly-Tyr-Val-Thr-Glu-Val(123)-OH (Fas14p) sequence of F. gigantica cathepsin L-cysteine proteinase. This sequence was synthesized in three different forms: as N(alpha) acetylated (Ac-Asp(110)-Lys-Ile-Asp-Trp-Arg-Glu-Ser-Gly-Tyr-Val-Thr-Glu-Val(123)-OH, FasAc14p), bearing at the amino-terminus an N(alpha) acetylated cystein (Ac-Cys-Asp(110)-Lys-Ile-Asp-Trp-Arg-Glu-Ser-Gly-Tyr-Val-Thr-Glu-Val(123)-OH, FasAcCys14p), and conjugated to sequential oligopeptide carrier Ac-[Lys-Aib-Gly](4)-OH (Ac-SOC(4)) through an amide bond formed between Val(123) carboxylic group of the epitope and the lysine N(epsilon) groups of the carrier (Ac-[Lys(Fas14p)-Aib-Gly](4)-OH). Ac-[Lys(Fas14p)-Aib-Gly](4)-OH failed to readily discriminate between naïve and infected sheep. In contrast, the free peptides reproducibly differentiated between parasite-free sheep, sheep infected with parasites other than Fasciola, and experimentally Fasciola-infected sheep. The data together indicated that the peptides might be of considerable use for discriminating between early and late, and low and high burden, sheep infection with F. gigantica. FasAc14p was chosen to determine whether a peptide based on a critical enzymatic site of cathepsin L proteinase may induce protection against challenge infection. Sheep immunization with FasAc14p peptide induced significant expression of interleukin-4 mRNA, and humoral antibodies that bound to molecule(s) on the intact surface membrane of newly excysted juvenile worms, and mediated their attrition. The immune responses were associated with significant (P < 0.02) decrease of 23.1% in worm recovery, but with no decrease in the size or maturation of worms recovered.