Synthesis of dinitrophenyltetrapeptides as chromophoric substrates of endoproteinases

The synthesis has been performed of ten tetrapeptides of the general formula Dnp-Gly-Gly-X-Arg-OH, where X = Val, Phe, Abu, Asp (OBut), Asp, Met, D-Phe, Ser, Thr, or Trp. The synthesis was carried out with Dnp-Gly-Gly-ONp, activated esters of protected amino acids, and arginine with an unprotected carboxy group. The coefficients of molar extinction of the tetrapeptides at 660 nm are given. It has been shown that the peptides can be used to determine the activities of neutral and alkaline proteinases from various sources, the peptides with X = Phe, Met, and Abu exhibiting the highest sensitivity to enzymatic hydrolysis.