Barns R J, Elmslie R G
Biochim Biophys Acta. 1976 Nov 8;452(1):161-4. doi: 10.1016/0005-2744(76)90067-x.
Calcium ions are shown to have a marked pH-dependent effect on the kinetics of benzoyllarginine ethyl ester hydrolysis by porcine enteropeptidase (EC 3.4.21.9). Below pH 6.0, calcium ions stimulate benzoylarginine ethyl ester hydrolysis but inhibit this activity above pH 6.0. This effect is mainly on the Km for benzoylarginine ethyl ester. At pH 5.3, 2mM calcium ions reduce the Km for benzoylarginine ethyl ester from 0.31 mM to 0.26 mM while at pH 6.5 the Km increases four-fold from 0.035 mM to 0.12 mM in the presence of calcium ions. Enteropeptidase activity is not inhibited by ethylenediaminetetra-acetate indicating that calcium ions are a non-essential cofactor for benzoylarginine ethyl ester hydrolysis.
钙离子对猪肠肽酶（EC 3.4.21.9）催化苯甲酰精氨酸乙酯水解的动力学具有显著的pH依赖性效应。在pH 6.0以下，钙离子刺激苯甲酰精氨酸乙酯的水解，但在pH 6.0以上则抑制该活性。这种效应主要体现在苯甲酰精氨酸乙酯的米氏常数（Km）上。在pH 5.3时，2mM钙离子使苯甲酰精氨酸乙酯的Km从0.31mM降至0.26mM，而在pH 6.5时，在钙离子存在下，Km从0.035mM增加四倍至0.12mM。乙二胺四乙酸不抑制肠肽酶活性，表明钙离子是苯甲酰精氨酸乙酯水解的非必需辅因子。
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