Kinetics of Chitinase from Yam, Dioscorea opposita THUNB
Kinetics of Chitinase from Yam, Dioscorea opposita THUNB
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山药、薯蓣THUNB几丁质酶的动力学
DOI：
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发表时间：
1989
期刊：
影响因子：
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通讯作者：
A. Ide
中科院分区：
文献类型：
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作者：
D. Koga;T. Tsukamoto;Nobuyuki Sueshige;T. Utsumi;A. Ide
以N-乙酰基壳低聚糖(GlcNAc“，/i=2~6)和β-硝基苯基N-乙酰基壳低聚糖(PNP-GlcNac”，w=1~5)为底物，对山药几丁质酶E3(EC3.2.1.14)进行了动力学分析。该酶通过三种途径将GlcNAc3裂解为GlcNAc+GlcNAc2，G1cNAc4裂解为GlcNAc2，GlcNAc5裂解为GlcNAc2+GlcNAc3，GlcNAc6裂解为GlcNAc+GlcNAc5(32%)、GlcNAc2+GlcNAc4(42%)和两个GlcNAc3(26%)。反应速度顺序为：GlcN AC4>；GlcN AC5>；GlcNAc6>；GlcN AC3。链长的底物具有较强的底物抑制作用。PNP-GlcNAcw(N=1~5)与GlcNAc“(N=2~6)的反应类似。PNP-GlcNAc2和PnP-GlcNAc3的裂解中心是从还原端侧起的第二个β-1，4-键，而PNP-GlcNAc4和PNP-GlcNAc5的主要裂解中心是第三个键。β-硝基苯酚并不是从所有β-硝基化合物中释放出来的。
Kinetic analysis was done on chitinase E3 (EC 3.2.1.14) from yam, Dioscorea opposita Thunb, using both series of N-acetylchitooligosaccharides (GlcNAc„, /i = 2 to 6) and β-nitrophenyl N- acetylchitooligosaccharides (pNp-GlcN Ac„, w= 1 to 5) as substrates. The enzyme cleaved GlcNAc3 to GlcNAc plus GlcNAc2, G1cNAc4 to two molecules of GlcNAc2, GlcNAc5 to GlcNAc2 plus GlcNAc3, and GlcNAc6 by three ways to GlcNAc plus GlcNAc5 (32 %), GlcNAc2 plus GlcNAc4 (42 %) and two molecules of GlcNAc3 (26%). The speed of the reaction was observed in the following order, GlcN Ac4 > GlcN Ac5 > GlcNAc6 > GlcN Ac3. Stronger substrate inhibition was observed in the longer chain substrates. The reactions of pNp-GlcNAcw (N = 1 to 5) were similar to those of GlcNAc„ (N = 2 to 6), respectively. The cleavage sites of pNp-GlcNAc2 and pNp-GlcNAc3 were the second β-1,4-linkages from the reducing end side, and the main cleavage sites of pNp-GlcNAc4 and pNp-GlcNAc5 were the third linkages. β-Nitrophenol was not released from all β-nitr...