- Kinetic study on conformational effect in hydrolysis of p-nitroanilides catalyzed by α-chymotrypsin
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Effects of medium viscosity on kinetics for the hydrolysis of p-nitroanilides of certain amino acid derivatives catalyzed by α-chymotrypsin have been investigated. Observed data indicate that the overall rate constant, kcat, is hardly affected by the medium viscosity in all the substrates employed and equals the rate constant at the acylation step, k2, in the measured range of viscosity. By comparison with the data on p-nitrophenyl ester substrates reported previously, it is concluded that the formation of the tetrahedral intermediate in the course of the acylation of the enzyme is influenced by conformational change of the enzyme, whereas the breakdown of the intermediate is almost free from conformational effects.
- Kawai, Yasushi,Matsuo, Takashi,Ohno, Atsuyoshi
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p. 887 - 891
(2007/10/03)
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- Purification and Some Properties of a Protease from the Sarcocarp of Musk Melon Fruit
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A protease has been purified from sarcocarp of musk melon.Cucumis melo ssp. melo var. reticulatus Naud.Earl's Favourite.The protease was mostly present in the placenta part of the fruit and next in the inside mesocarp.The molecular mass of the enzyme was estimated to be about 62 kDa on SDS-PAGE.The enzyme had a carbohydrate moiety.The optimum pH of the enzyme was 11 at 35 deg C using casein as a substrate.The enzyme was stable between pH 6 and 11.The enzyme was strongly inhibited by diisopropyl fluorophosphate, but was not inhibited by EDTA or cysteine protease inhibitors.From the digestion of Ala-Ala-Pro-X-pNA (X = Phe, Leu, Val, Ala, Gly, Lys, Glu, Pro, and diaminopropionic acid (Dap) substrates the specificity of the protease was found to be approximately broad, but the preferential cleavage sites were C-terminal sites of h)drophobic or acidic amino acid residues at P1 position.It was proved that the enzymatic properties of musk melon protease are similar to those of cucumisin .The enzvme was not inhibited by typical proteinous inhibitors such as STI or ovomucoid.Therefore, this enzyme seems to be a useful protease for the food industries. - Keywords: Cucumis melo; Cucurbitaceae; musk melon; plant protease; serine protease.
- Kaneda, Makoto,Yonezawa, Hiroo,Uchikoba, Tetsuya
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p. 2100 - 2102
(2007/10/03)
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