The inhibitory effect of various substances on an immobilized derivative of carboxypeptidase C
N (AEC-CPase C
N), which was prepared by conjugating the enzyme to AE-cellulose through glutaraldehyde, was examined. Like the native enzyme, AEC-CPase C
N was inactivated by methanol and this inactivation became more pronounced as the concentration of methanol increased. AEC-CPase C
N was slightly more stable to the attack of Pronase than the native enzyme. Enzymic activity of AEC-CPase C
N was completely loss by the addition of low concentrations of sodium dodecyl sulfate and cetyltrimethylammonium bromide, whereas Triton X-100 and Tween 80 caused only a partial loss of the enzymic activity even at high concentrations. Of six phenylalanine analogs tested, β-phenylpropionic acid, a competitive inhibitor, showed the most inhibitory effect. Pretreatment of AEC-CPase C
N with 25 mM β-phenylpropionic acid almost completely protected the enzyme from inactivation by diisopropylfluorophosphate, while the attack of p-bromophenacyl bromide and HgCl
2. was only partially blocked by the same pretreatment. The denaturating effect of methanol, heat, and pH was not prevented by the pretreatment with β-phenylpropionic acid.
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