Glycogen debranching enzyme (GDE), together with glycogen phosphorylase (GP), is responsible for the complete degradation of glycogen. GDE has distinct catalytic sites for 4-α-glucanotransferase and amylo-α-1,6-glucosidase. For the GDE sensitive assay, we previously developed the GP limit fluorogenic branched dextrin Glcα1–4Glcα1–4Glcα1–4Glcα1–4(Glcα1–4Glcα1–4Glcα1–4Glcα1–6)Glcα1–4Glcα1–4Glcα1–4GlcPA (B4/84, where Glc = d-glucose and GlcPA = 1-deoxy-1-[(2-pyridyl)amino]-d-glucitol). However, B4/84 is not widely available because of difficulties in its chemical synthesis and positional-isomer separation (0.33% yield by α-1,6-coupling of maltotetraose with Glc₇-GlcPA). In this study, we attempted to develop an efficient method for the preparation of Glcα1–4Glcα1–4Glcα1–4Glcα1–4(Glcα1–4Glcα1–4Glcα1–4Glcα1–6)Glcα1–4Glcα1–4GlcPA (B3/74), which was designed to have the minimum essential dextrin structure for GDE. First, Glcα1–6Glcα1–4Glcα1–4GlcPA (B3/31) was prepared from commercially available Glcα1–6Glcα1–4Glcα1–4Glc. Using α-cyclodextrin as a donor substrate, cyclodextrin glucanotransferase elongated both the main and side branches on B3/31, while all the glycosidic bonds in B3/31 were left intact. After exhaustive digestion with GP, B3/74 was obtained from B3/31 with 16% yield, a value that is 48-fold greater than that previously reported for B4/84. GDE 4-α-glucanotransferase exhibited high activity toward both B3/74 and B4/84. In addition, we studied the efficient conversion of B3/74 into Glcα1–4Glcα1–4Glcα1–4Glcα1–4(Glcα1–6)Glcα1–4Glcα1–4GlcPA (B3/71), which has the best dextrin structure for the GDE amylo-α-1,6-glucosidase.

糖原脱支酶 (GDE) 与糖原磷酸化酶 (GP) 一起负责糖原的完全降解。GDE 对 4-α-葡聚糖转移酶和淀粉-α-1,6-葡糖苷酶具有不同的催化位点。对于 GDE 敏感测定，我们之前开发了 GP 限制荧光支化糊精 Glcα1–4Glcα1–4Glcα1–4Glcα1–4(Glcα1–4Glcα1–4Glcα1–4Glcα1–6)Glcα1–4Glcα1–4Glcα1–4Glc4, 其中 Glcα1–4Glcα1–4Glc4  ð葡萄糖和GlcPA = 1-脱氧-1 - [（2-吡啶基）氨基] - d -glucitol）。然而，B4/84 由于其化学合成和位置异构体分离困难（麦芽四糖与 Glc ₇ α-1,6-偶联的产率为 0.33%-GlcPA)。在本研究中，我们试图开发一种制备 Glcα1–4Glcα1–4Glcα1–4Glcα1–4(Glcα1–4Glcα1–4Glcα1–4Glcα1–6)Glcα1–4Glcα1–4GlcPA (B3/74) 的有效方法，该方法旨在具有 GDE 的最小必需糊精结构。首先，Glcα1-6Glcα1-4Glcα1-4GlcPA (B3/31) 由市售的 Glcα1-6Glcα1-4Glcα1-4Glc 制备。使用 α-环糊精作为供体底物，环糊精葡糖基转移酶延长了 B3/31 上的主支和侧支，而 B3/31 中的所有糖苷键保持完整。用 GP 彻底消化后，从 B3/31 中获得了 B3/74，产率为 16%，比之前报道的 B4/84 值高 48 倍。GDE 4-α-葡聚糖转移酶对 B3/74 和 B4/84 均表现出高活性。此外，