Duroux L, Delmotte F M, Lancelin J M, Kéravis G, Jay-Allemand C
Station d'Amélioration des Arbres Forestiers, I.N.R.A.-Orléans, 45160 Ardon, France.
Biochem J. 1998 Jul 15;333 ( Pt 2)(Pt 2):275-83. doi: 10.1042/bj3330275.
In plants, the naphthoquinone juglone is known to be involved in pathogenic defence mechanisms, but it may also take part in plant developmental processes. This naphthoquinone can accumulate in a glycosylated form, namely hydrojuglone beta-d-glucopyranoside. The structural configuration of this compound was shown to be 1, 5-dihydroxy-4-naphthalenyl-beta-d-glucopyranoside by means of MS, NMR and nuclear Overhauser effect spectroscopy analyses. A hydrojuglone beta-d-glucopyranoside beta-glucosidase (EC 3.2.1.21) was purified to homogeneity from Juglans regia L. The enzyme catalysed the release of juglone from hydrojuglone beta-d-glucopyranoside with high specificity and showed Michaelis-Menten kinetics with Km=0.62 mM and Vmax=14.5 microkat/mg of protein. This enzyme also showed a higher activity towards beta-d-fucosyl than beta-d-glucosyl bonds. The purified enzyme had an apparent Mr of 64000 by SDS/PAGE and a pI 8.9 by isoelectrofocusing PAGE. The purified enzyme was inhibited by several bivalent cations, such as Cu2+, Fe2+, Hg2+, and by d-glucono-1,5-lactone, showing non-competitive inhibition of the mixed type.
在植物中，已知萘醌胡桃醌参与致病防御机制，但它也可能参与植物发育过程。这种萘醌可以以糖基化形式积累，即氢化胡桃醌β -D-吡喃葡萄糖苷。通过质谱（MS）、核磁共振（NMR）和核Overhauser效应光谱分析表明，该化合物的结构构型为1,5 -二羟基-4 -萘基-β -D-吡喃葡萄糖苷。从胡桃（Juglans regia L.）中纯化出一种氢化胡桃醌β -D-吡喃葡萄糖苷β -葡萄糖苷酶（EC 3.2.1.21），使其达到同质。该酶能以高特异性催化从氢化胡桃醌β -D-吡喃葡萄糖苷中释放出胡桃醌，并表现出米氏动力学，Km = 0.62 mM，Vmax = 14.5微卡特/毫克蛋白质。该酶对β -D-岩藻糖基键的活性也高于β -D-葡萄糖基键。通过十二烷基硫酸钠/聚丙烯酰胺凝胶电泳（SDS/PAGE）测定，纯化后的酶表观分子量为64000，通过等电聚焦聚丙烯酰胺凝胶电泳测定其等电点为8.9。纯化后的酶受到几种二价阳离子的抑制，如Cu2 +、Fe2 +、Hg2 +，以及受到D-葡萄糖酸-1,5-内酯的抑制，表现出混合型非竞争性抑制。
