Bax Hilda Hubertha Maria, van der Maarel Marc Jos Elise Cornelis, Jurak Edita
Bioproduct Engineering, Engineering and Technology Institute Groningen, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
Polymers (Basel). 2023 Jun 22;15(13):2777. doi: 10.3390/polym15132777.
Starch-like polymers can be created through the use of enzymatic modification with glycogen branching enzymes (GBEs). GBEs are categorized in the glycoside hydrolase (GH) family 13 and 57. Both GH13 and GH57 GBEs exhibit branching and hydrolytic activity. While GH13 GBEs are also capable of α-1,4-transglycosylation, it is yet unknown whether GH57 share this capability. Among the four crystal structures of GH57 GBEs that have been solved, a flexible loop with a conserved tyrosine was identified to play a role in the branching activity. However, it remains unclear whether this flexible loop is also involved in α-1,4-transglycosylation activity. We hypothesize that GH57 GBEs with the flexible loop and tyrosine are also capable of α-1,4-transglycosylation, similar to GH13 GBEs. The aim of the present study was to characterize the activity of GH57 GBEs to investigate a possible α-1,4-transglycosylation activity. Three GH57 GBEs were selected, one from with the flexible loop and two beta-strands; one from , missing the flexible loop and beta-strands; and one from sp., missing the flexible loop but with the two beta-strands. The analysis of chain length distribution over time of modified maltooctadecaose, revealed, for the first time, that all three GH57 GBEs can generate chains longer than the substrate itself, showing that α-1,4-transglycosylation activity is generally present in GH57 GBEs.
通过使用糖原分支酶（GBEs）进行酶促修饰，可以生成淀粉样聚合物。GBEs被归类于糖苷水解酶（GH）家族13和57。GH13和GH57 GBEs都具有分支和水解活性。虽然GH13 GBEs也能够进行α-1,4-转糖基化，但尚不清楚GH57是否具有这种能力。在已解析的四种GH57 GBEs晶体结构中，发现一个带有保守酪氨酸的柔性环在分支活性中起作用。然而，尚不清楚这个柔性环是否也参与α-1,4-转糖基化活性。我们假设具有柔性环和酪氨酸的GH57 GBEs也能够进行α-1,4-转糖基化，类似于GH13 GBEs。本研究的目的是表征GH57 GBEs的活性，以研究其可能的α-1,4-转糖基化活性。选择了三种GH57 GBEs，一种来自具有柔性环和两条β链的；一种来自缺少柔性环和β链的；一种来自某物种，缺少柔性环但有两条β链。对修饰的麦芽十八糖随时间的链长分布分析首次表明，所有三种GH57 GBEs都能生成比底物本身更长的链，这表明α-1,4-转糖基化活性普遍存在于GH57 GBEs中。
