Benzoate-Coenzyme A ligase enzyme activity catalyzing the conversion of free benzoic acid to benzoyl-CoA was detected and biochemically characterized in the elicitor-treated pear cell cultures. Asian pear (Pyrus pyrifolia) is an economically and nutritionally important fruit-bearing tree of the subtribe Malinae. Upon pathogen attack, pears produce unique benzoate-derived biphenyl phytoalexins. The upstream biosynthesis of the biphenyl in Malinae is still incomplete. Previously, protein preparations from yeast extract-treated pear cultures were able to convert L-phenylalanine to cinnamic acid catalyzed by the activity of the phenylalanine ammonia lyase. The same extract was able to perform a C2 side-chain cleavage of cinnamic acid to benzaldehyde followed by oxidation of the latter to benzoic acid owing to the molecularly-undefined benzaldehyde synthase and benzaldehyde dehydrogenase activities, respectively. The biosynthesis of biphenyls starts with benzoate-Coenzyme A ligase (BZL), which converts benzoic acid to benzoyl-CoA. Subsequently, the previously-defined biphenyl synthase uses benzoyl-CoA to form the biphenyls. The current study reports the first time detection and characterization of BZL activity in elicitor-treated pear cell cultures. The preferred substrate was benzoic acid (Km = 62 ± 4 µM). Magnesium or manganese was prerequisite for the activity, which was enhanced by ~ 70% in the presence of potassium. Maximum BZL activity was observed 18 h post elicitation, which is in agreement with the coordinate induction reported for the enzymes in the same pathway. The induced BZL activity preceded the accumulation of biphenyls supporting its involvement in their biosynthesis.

中文翻译：

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苯甲酸-CoA 连接酶有助于诱导剂处理的梨细胞培养物中联苯植物抗毒素的生物合成。

在诱导剂处理的梨细胞培养物中检测到催化游离苯甲酸转化为苯甲酰辅酶 A 的苯甲酸辅酶 A 连接酶活性，并对其进行生化表征。亚洲梨 (Pyrus pyrifolia) 是马林亚科的经济和营养重要的结果树。在病原体攻击时，梨会产生独特的苯甲酸盐衍生的联苯植物抗毒素。Malinae中联苯的上游生物合成仍然不完整。以前，来自酵母提取物处理的梨培养物的蛋白质制剂能够通过苯丙氨酸解氨酶的活性将 L-苯丙氨酸转化为肉桂酸。由于分子不确定的苯甲醛合酶和苯甲醛脱氢酶的活性，相同的提取物能够将肉桂酸的 C2 侧链裂解为苯甲醛，然后将后者氧化为苯甲酸。联苯的生物合成始于苯甲酸辅酶 A 连接酶 (BZL)，它将苯甲酸转化为苯甲酰辅酶 A。随后，先前定义的联苯合酶使用苯甲酰-CoA 形成联苯。目前的研究报告了在诱导剂处理的梨细胞培养物中首次检测和表征 BZL 活性。优选的底物是苯甲酸 (Km = 62 ± 4 µM)。镁或锰是该活性的先决条件，在钾的存在下可提高约 70%。激发后 18 小时观察到最大 BZL 活性，这与针对同一途径中的酶报道的协调诱导一致。诱导的 BZL 活性先于联苯的积累，支持其参与其生物合成。