Viruses are a heterogeneous ensemble of entities, all sharing the need for a suitable host to replicate. They are extremely diverse, varying in morphology, size, nature, and complexity of their genomic content. Typically, viruses use host-encoded glycosyltransferases and glycosidases to add and remove sugar residues from their glycoproteins. Thus, the structure of the glycans on the viral proteins have, to date, typically been considered to mimick those of the host. However, the more recently discovered large and giant viruses differ from this paradigm. At least some of these viruses code for an (almost) autonomous glycosylation pathway. These viral genes include those that encode the production of activated sugars, glycosyltransferases, and other enzymes able to manipulate sugars at various levels. This review focuses on large and giant viruses that produce carbohydrate-processing enzymes. A brief description of those harboring these features at the genomic level will be discussed, followed by the achievements reached with regard to the elucidation of the glycan structures, the activity of the proteins able to manipulate sugars, and the organic synthesis of some of these virus-encoded glycans. During this progression, we will also comment on many of the challenging questions on this subject that remain to be addressed.

中文翻译：

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巨型病毒中令人惊叹的聚糖世界


病毒是实体的异构集合，所有病毒都需要合适的宿主来进行复制。它们极其多样化，在形态、大小、性质和基因组内容的复杂性方面各不相同。通常，病毒使用宿主编码的糖基转移酶和糖苷酶来添加和去除其糖蛋白中的糖残基。因此，迄今为止，病毒蛋白上的聚糖结构通常被认为是模仿宿主的聚糖结构。然而，最近发现的大型和巨型病毒与这种范式不同。这些病毒中至少有一些编码（几乎）自主的糖基化途径。这些病毒基因包括编码产生活化糖、糖基转移酶和其他能够在不同水平上操纵糖的酶的基因。这篇综述重点关注产生碳水化合物加工酶的大型和巨型病毒。将讨论在基因组水平上具有这些特征的病毒的简要描述，然后讨论在聚糖结构的阐明、能够操纵糖的蛋白质的活性以及其中一些病毒的有机合成方面所取得的成就-编码聚糖。在此过程中，我们还将评论有关该主题的许多有待解决的挑战性问题。