Manganese-dependent inhibition of human liver arginase by borate
Manganese-dependent inhibition of human liver arginase by borate
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DOI：
10.1016/s0162-0134(99)00187-7
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发表时间：
1999-11-01
影响因子：
3.9
通讯作者：
Fuentes, M
中科院分区：
文献类型：
--
作者：
Carvajal, N;Salas, M;Fuentes, M
通过在60 ℃下与5 mM Mn（2+）孵育10分钟完全激活人肝脱氢酶（EC 3.5.3.1），导致V（max）增加和酶对硼酸盐抑制的更高灵敏度，而精氨酸的K（m）没有变化。硼酸盐表现为S-双曲线I-双曲线非竞争性抑制剂，并且对酶与竞争性抑制剂L-鸟氨酸（K（i）= 2 +/- 0.5 mM）、L-赖氨酸（K（i）= 2.5 +/- 0.4 mM）和氯化胍（K（i）= 100 +/- 10 mM）的相互作用没有影响。抑制的pH依赖性与四面体B（OH）（4）（-）是抑制剂一致，而不是三角形B（OH）（3）。我们认为，脱氢酶活性与紧密结合的Mn（2+）有关，其催化作用可通过加入更松散结合的Mn（2+）来刺激，以产生完全活化的酶形式。硼酸盐抑制的Mn（2+）依赖性和部分特征通过假设硼酸盐与松散结合的Mn（2+）紧密结合并干扰其刺激作用来解释。虽然硼酸盐可以防止焦碳酸二乙酯（DEPC）对酶的失活，但DEPC敏感的残基不被认为是硼酸盐结合的配体，因为保留约10%酶活性的化学修饰物种也对抑制剂敏感。（C）1999年Elsevier Science Inc. All rights reserved.
Full activation of human liver arginase (EC 3.5.3.1), by incubation with 5 mM Mn(2+) for 10 min at 60 degrees C, resulted in increased V(max) and a higher sensitivity of the enzyme to borate inhibition, with no change in the K(m) for arginine. Borate behaved as an S-hyperbolic I-hyperbolic non-competitive inhibitor and had no effect on the interaction of the enzyme with the competitive inhibitors L-ornithine (K(i) = 2 +/- 0.5 mM), L-lysine (K(i) = 2.5 +/- 0.4 mM), and guanidinium chloride (K(i) = 100 +/- 10 mM). The pH dependence of the inhibition was consistent with tetrahedral B(OH)(4)(-) being the inhibitor, rather than trigonal B(OH)(3). We suggest that arginase activity is associated with a tightly bound Mn(2+) whose catalytic action may be stimulated by addition of a more loosely bound Mn(2+), to generate a fully activated enzyme form. The Mn(2+) dependence and partial character of borate inhibition are explained by assuming that borate binds in close proximity to the loosely bound Mn(2+) and interferes with its stimulatory action. Although borate protects against inactivation of the enzyme by diethyl pyrocarbonate (DEPC), the DEPC-sensitive residue is not considered as a ligand for borate binding, since chemically modified species, which retain about 10% of enzymatic activity, were also sensitive to the inhibitor. (C)1999 Elsevier Science Inc. All rights reserved.