Abstract:
The purpose of this work was to study on active site at S,-subsite position of actinidain, isolatedfrom kiwifruit (Actinidia chinensis).The actinidain was purified to homogeneity in a single step bycovalent chromatography with thiopropyl gel column. The enzyme has a molecular weight of 27kDa. The thiol content of the enzyme at pH 4 and 8 were 1 and 0.93, respectively. The pnitroanilidederivative substrate, N-Ac-L-Phe-Gly-p-nitroanilide, N-Ac-L-Phe-Leu-p-nitroanilide,N-Ac-L-Phe-Phe-p-nitroanilide, N-Ac-L-Phe-Arg-p-nitroanilide and N-Ac-L-Phe-Glu-p-nitroanilidewere synthesized in our laboratory and proved to be pure forms by melting point, optical rotation,mass spectrometry, 'H-NMR spectroscopy and elemental analysis. Kinetic study showed that thekeat/Km of the purified actinidain toward N-Ac-L-Phe-Gly-p-nitroanilide, N-Ac-L-Phe-Leu-pnitroanilide,N-Ac-L-Phe-Phe-p-nitroanilide, N-Ac-L-Phe-Arg-p-nitroanilide were 34.92, 47.60,69.10 and 2.6 mMกำลัง-1sกำลัง-1, respectively, whereas actinidain had very low activity toward N-Ac-L-Phe-Glu-p-nitroanilide. This result revealed the presence of the deeply hydrophobic pocket at S,-subsiteposition of the active site of actinidain.