Abstract:
The aim of the work presented in this thesis was to study active site at S,-subsite position of purifiedpapain with synthesizedp-nitroanilide derivative substrates. Papain was extracted from the latex ofthe unripe papaya fruits (Carica papaya L.). It was mixed with saturation 2,2'-dypyridyl disulphide(2PDS) immediately for antiautolysis. Papain was purified by the fast protein liquidchromatography (FPLC) with a Hiload 26/10 SP-Sepharose HP column and showed only oneband on SDS-PAGE, with a low molecular mass of purified papain was estimated at 29 kilo-daltons.The p-nitroanilide derivative substrate, N-Ac-L-Phe-Gly-pNA, N-Ac-L-Phe-Leu-pNA,N-Ac-L-Phe-Arg-pNA, N-Ac-L-Phe-Phe-pNA and N-Ac-L-Phe-Glu-pNA were synthesized in ourlaboratory and proved to be pure forms by thin-layer chromatography, optical rotation,nuclear magnetic resonance, mass spectroscopy and elemental analysis. The kinetic study showedthat the kc,JKm of purified papain toward N-Ac-L-Phe-Gly-pNA, N-Ac-L-Phe-Leu-pNA,N-Ac-L-Arg-Phe-pNA and N-Ac-L-Phe-Phe-pNA were 269.77, 1367.00, 1469.37 and473.49 Mกำลัง-1'.sde]y'-1, respectively, except N-Ac-L-Phe-Glu-pNA whereas papain activity toward saturatedNAc-L-Phe-Glu-pNA at 0.05 dA,,drnin. The result reveals the broad specificity of S1-subsitepocket located inside the active site of papain.