Biosynthesis of truncated N-linked oligosaccharides results from non-orthologous hexosaminidase-mediated mechanisms in nematodes, plants, and insects.
Biosynthesis of truncated N-linked oligosaccharides results from non-orthologous hexosaminidase-mediated mechanisms in nematodes, plants, and insects.
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DOI：
10.1074/jbc.m704235200
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发表时间：
2007-09-21
期刊：
影响因子：
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通讯作者：
Wilson IB
中科院分区：
文献类型：
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作者：
Gutternigg M;Kretschmer-Lubich D;Paschinger K;Rendić D;Hader J;Geier P;Ranftl R;Jantsch V;Lochnit G;Wilson IB
在许多无脊椎动物和植物中，n -糖基化谱主要由截断的少糖苷型n -聚糖组成，即由简单的三糖基壳生物基核心组成的聚糖，通常被核心聚焦残基修饰。尽管它们缺乏触角n -乙酰氨基葡萄糖残基，但这些聚糖的生物合成需要GlcNAc转移酶I、高尔基甘露糖苷酶II以及最后的β- n -乙酰氨基葡萄糖酶的连续作用。在果蝇中，最近发现的由融合叶（fdl）基因编码的酶特异性地从n-聚糖的α1,3天线中去除非还原的n-乙酰氨基葡萄糖残基。在本研究中，我们检测了秀丽隐杆线虫（Caenorhabditis elegans）中5个β- n -乙酰己糖氨酸酶基因（hexx -1至hexx -5）的产物，对应阅读框T14F9.3, C14C11.3, Y39A1C。4, Y51F10.5和Y70D2A.2)，另外还有3个来自拟南芥（AtHEX1， AtHEX2和AtHEX3，分别对应阅读框At1g65590， At3g55260和At1g05590）。基于同源性，Caenorhabditis hexx -1和所有三种拟南芥酶与上述果蝇融合叶酶是同一亚家族的成员，但要么作为壳三酸苷酶，要么非特异性地从两个n-聚糖触角上去除n-乙酰氨基葡萄糖。其他四种隐杆线虫酶是一个不同亚家族的成员；然而，其中两种酶表现出与融合叶酶相同的α1,3-触角特异性。此外，Caenorhabditis hexx -2基因的部分缺失大大降低了突变蠕虫提取物中天然n-聚糖特异性己糖氨酸酶的活性，并导致n-聚糖谱的改变，这证明了其体内酶的相关性。基于这些数据，我们假设线虫、植物和昆虫中少糖苷聚糖的遗传起源涉及同一己糖胺酶基因家族的高度分化成员。
In many invertebrates and plants, the N-glycosylation profile is dominated by truncated paucimannosidic N-glycans, i.e., glycans consisting of a simple trimannosylchitobiosyl core often modified by core fucose residues. Even though they lack antennal N-acetylglucosamine residues, the biosynthesis of these glycans requires the sequential action of GlcNAc transferase I, Golgi mannosidase II and, finally, β-N-acetylglucosaminidases. In Drosophila, the recently characterised enzyme encoded by the fused lobes (fdl) gene specifically removes the non-reducing N-acetylglucosamine residue from the α1,3-antenna of N-glycans. In the present study, we examined the products of five β-N-acetylhexosaminidase genes from Caenorhabditis elegans (hex-1 to hex-5, corresponding to reading frames T14F9.3, C14C11.3, Y39A1C.4, Y51F10.5 and Y70D2A.2) in addition to three from Arabidopsis thaliana (AtHEX1, AtHEX2 and AtHEX3, corresponding to reading frames At1g65590, At3g55260 and At1g05590). Based on homology, the Caenorhabditis HEX-1 and all three Arabidopsis enzymes are members of the same sub-family as the aforementioned Drosophila fused lobes enzyme, but either act as chitotriosidases or non-specifically remove N-acetylglucosamine from both N-glycan antennae. The other four Caenorhabditis enzymes a members of a distinct sub-family; nevertheless, two of these enzymes displayed the same α1,3-antennal specificity as the fused lobes enzyme. Furthermore, a deletion of part of the Caenorhabditis hex-2 gene drastically reduces the native N-glycan-specific hexosaminidase activity in mutant worm extracts and results in a shift in the N-glycan profile, which is a demonstration of its in vivo enzymatic relevance. Based on these data, it is hypothesised that the genetic origin of paucimannosidic glycans in nematodes, plants and insects involves highly-divergent members of the same hexosaminidase gene family.