Characterization and kinetic analysis of indolamine N-acetyltransferase from the collaterial glands of the American cockroach, Periplaneta americana
Characterization and kinetic analysis of indolamine N-acetyltransferase from the collaterial glands of the American cockroach, Periplaneta americana
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DOI：
10.1303/aez.33.127
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发表时间：
1998-02-01
影响因子：
1.3
通讯作者：
Takeda, M
中科院分区：
文献类型：
--
作者：
Asano, H;Takeda, M
对美洲大蠊雌性生殖腺吲哚胺N-乙酰转移酶（NAT）的酶学性质和动力学进行了分析。活性仅限于附属腺，在卵巢中未发现活性。该酶显示出两个最适pH，即，6.0 9.0-9.5。在较高的pH范围内的最佳值发生在略有不同的pH值，这取决于底物; 9.5与色胺（TP）和9.0与5-羟色胺（5 HT）。表观动力学参数如下：TP的Km为45 μ M，V-max为6.87 nmol产物/mg蛋白/min，而5 HT的Km为190 μ M，V-max为41.0 nmol产物/mg蛋白/min。乙酰辅酶A的Km为58 μ M，V-max为6.88 nmol/mg蛋白/min，而5-HT的K-m为120 μ M，V-max为41.3 nmol/mg/min。动力学分析表明，底物结合的进展，根据一个连续的Bi-Bi机制，不像NAT的情况下，从头神经节。
Enzyme properties and kinetics of indolamine N-acetyltransferase (NAT) from female reproductive glands of Periplaneta americana were analyzed. The activity was restricted to the accessory glands and no activity was found in the ovary. The enzyme showed two pH optima, i.e., 6.0 and 9.0-9.5. The optimum at a higher pH range occurred at slightly different pHs depending an the substrate; 9.5 with tryptamine (TP) and 9.0 with serotonin (5HT). Apparent kinetic parameters were as follows; the K-m for TP was 45 mu M and the V-max 6.87 nmol product/mg protein/min, whereas the K-m for 5HT was 190 mu M and the V-max 41.0 nmol product/mg protein/min. The K-m for acetyl-CoA was 58 mu M and the V-max 6.88 nmol/mg/min with TP, whereas the K-m 120 mu M and the V-max 41.3 nmol/mg/min with 5HT. The kinetic analysis suggests that substrate binding proceeds according to a sequential Bi-Bi mechanism unlike the case of NAT from the cephalic ganglia.