ニジマス,カツオ,およびアワビのβ-グルクロニダーゼの特性

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As reported previously4), β-glucuronidase is distributed widely in the fish tissues such as liver and kidney. In this paper, the properties of β-glucuronidase prepared from the liver of rainbow trout, skipjack and abalone were compared with that of the bovine liver enzyme. 1. The optimum pH of the fish enzyme is 4.5 which is not much different from the value for the mammalian enzyme, while the abalone enzyme exhibits its maximum activity at pH 3.6 (Fig. 3). 2. There is no extreme difference among the Km values of phenolphthalein-β-D-glucosiduronic acid and p-nitrophenyl-β-D-glucosiduronic acid for the enzymes from different sources (Table 2). 3. Arrhenius plot shows a downward bend at 30-40° (Fig. 6). The activation energy is 18, 000-20, 000cal./mole below the transition temperature for all enzymes, but the values above that temperature vary with the enzymes from different sources (Table 3). 4. The thermostability of the enzyme seems to be independent of the body temperature of animals from which the enzyme was prepared (Fig. 7). 5. The fish enzyme is inhibited competitively by glucaro-1, 4-lactone and noncompetitively by metal ions as seen with the mammalian enzyme (Figs. 9 and 11). The inhibition by metal ions is completely reversed by the addition of cysteine (Table 8). In general, there is no great difference among the Ki values of various inhibitors for the enzyme prepared from different sources (Tables 5 and 7). 6. The enzyme of rainbow trout is inhibited by DNA as well as by heparin (Table 9).

ニジマス,カツオ,およびアワビのβ-グルクロニダーゼの特性

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