DETECTION AND CHARACTERIZATION OF PARA-COUMARIC ACID HYDROXYLASE IN MUNG BEAN, VIGNA-MUNGO, SEEDLINGS
DETECTION AND CHARACTERIZATION OF PARA-COUMARIC ACID HYDROXYLASE IN MUNG BEAN, VIGNA-MUNGO, SEEDLINGS
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DOI：
10.1093/oxfordjournals.jbchem.a122651
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发表时间：
1989-02-01
影响因子：
2.7
通讯作者：
TAKEUCHI, W
中科院分区：
文献类型：
--
作者：
KOJIMA, M;TAKEUCHI, W
在用腱毒素（一种真菌毒素）处理的绿豆幼苗中检测到一种新的对香豆酸（4-羟基肉桂酸）羟化酶，其中在体外羟化多种单酚的多酚氧化酶被完全消除。该酶需要分子氧，最适 pH 值为 5.0。该酶仅作用于对香豆酸（Km，3.0×10-5 M），而其对电子供体的特异性相当广泛。 NADPH 的 Km 值 (1.5 × 10-4 M) 远低于 L-抗坏血酸 (1.0 × 10-2 M)，尽管两种电子供体的 Vmax 值几乎相同。该酶被β-巯基乙醇（Ki，3.5×10-6 M）和二乙基二硫代氨基甲酸酯（Ki，2.3×10-4 M）有效抑制，但对对氯汞苯甲酸酯不敏感。该酶位于细胞器中，在蔗糖密度梯度离心中沉积在线粒体和内质网之间。幼苗中的酶活性响应光的诱导而发生变化，这表明其参与了绿豆幼苗中酚类化合物的生物合成。
A new p-coumaric acid (4-hydroxycinnamic acid) hydroxylase was detected in mung bean seedlings treated with tentoxin, a fungal toxin, in which polyphenol oxidase that hydroxylates a wide variety of monophenols in vitro was completely eliminated. The enzyme required molecular oxygen and showed a pH optimum of 5.0. The enzyme acted only on p-coumaric acid (Km, 3.0 .times. 10-5 M), while its specificity for the electron donor was rather broad. The Km value for NADPH (1.5 .times. 10-4 M) was much lower than that for L-ascorbic acid (1.0 .times. 10-2 M), although the Vmax value was almost the same with both electron donors. The enzyme was potently inhibited by .beta.-mercaptoethanol (Ki, 3.5 .times. 10-6 M) and diethyldithiocarbamate (Ki, 2.3 .times. 10-4 M), but was insensitive to p-chloromercuribenzoate. The enzyme was localized in the cell organelles which sedimented between mitochondria and endoplasmic reticulum on sucrose density gradient centrifugation. The enzyme activity in the seedling was changed in response to induction by light in a manner suggesting its involvement in biosynthesis of phenolic compounds in mung bean seedlings.