Inversion of configuration during hydrolysis of alpha-1,4-galacturonidic linkage by three Aspergillus polygalacturonases
Inversion of configuration during hydrolysis of alpha-1,4-galacturonidic linkage by three Aspergillus polygalacturonases
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DOI：
10.1016/0014-5793(96)00171-8
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发表时间：
1996-03-18
期刊：
影响因子：
3.5
通讯作者：
Visser, J
中科院分区：
文献类型：
--
作者：
Biely, P;Benen, J;Visser, J
尼日尔曲霉的内切多聚半乳糖醛酸酶I和II（PGI和PG II）和A. tubingensis仅仅研究以揭示它们水解作用的立体化学。还原的五半乳糖醛酸（penta-GalU-ol）和还原的三半乳糖醛酸（triGalU-ol）用作酶的非还原底物。在D2 O反应混合物中形成的产物中的还原末端的构型随后通过H-1-NMR光谱进行。已经明确确定，pentaGalU-醇通过PGI和PGII的初级裂解导致二GalU-醇和triGalUA的β-异头物。通过ExoPG水解triGalU-醇的主要产物是diGalU-醇和GalUA的β-端基异构体。因此，所有三种曲霉属多聚半乳糖醛酸酶都属于所谓的转化聚糖酶，即它们利用糖苷键水解的单一置换机制。
Endopolygalacturonases I and II (PGI and PGII) of Aspergillus niger and an exopolygalacturonase (ExoPG) of A. tubingensis mere investigated to reveal the stereochemistry of their hydrolytic action. Reduced pentagalacturonic acid (penta-GalU-ol) and reduced trigalacturonic acid (triGalU-ol) were used as non-reducing substrates for the enzymes. The configuration of the reducing ends in the products formed in D2O reaction mixtures was followed by H-1-NMR spectroscopy. It has been unambiguously established that primary cleavage of pentaGalU-ol by both PGI and PGII leads to diGalU-ol and the p-anomer of triGalUA. The primary products of hydrolysis of triGalU-ol by ExoPG were diGalU-ol and the beta-anomer of GalUA. Thus, all three Aspergillus polygalacturonases belong to the so-called inverting glycanases, i.e. they utilize the single displacement mechanism of hydrolysis of the glycosidic linkage.