Li Busu, Meng Jie, Li Li, Liu Sheng, Wang Ting, Zhang Guofan
University of Chinese Academy of Sciences , Beijing 100049, China.
Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology , Qingdao 266000, China.
J Agric Food Chem. 2017 Sep 6;65(35):7764-7773. doi: 10.1021/acs.jafc.7b02720. Epub 2017 Aug 22.
High glycogen levels in the Pacific oyster (Crassostrea gigas) contribute to its flavor, quality, and hardiness. Glycogenin (CgGN) is the priming glucosyltransferase that initiates glycogen biosynthesis. We characterized the full sequence and function of C. gigas CgGN. Three CgGN isoforms (CgGN-α, β, and γ) containing alternative exon regions were isolated. CgGN expression varied seasonally in the adductor muscle and gonadal area and was the highest in the adductor muscle. Autoglycosylation of CgGN can interact with glycogen synthase (CgGS) to complete glycogen synthesis. Subcellular localization analysis showed that CgGN isoforms and CgGS were located in the cytoplasm. Additionally, a site-directed mutagenesis experiment revealed that the Tyr200Phe and Tyr202Phe mutations could affect CgGN autoglycosylation. This is the first study of glycogenin function in marine bivalves. These findings will improve our understanding of glycogen synthesis and accumulation mechanisms in mollusks. The data are potentially useful for breeding high-glycogen oysters.
太平洋牡蛎（Crassostrea gigas）中高含量的糖原有助于提升其风味、品质和耐寒性。糖原素（CgGN）是启动糖原生物合成的起始葡糖基转移酶。我们对太平洋牡蛎CgGN的完整序列和功能进行了表征。分离出了三种含有可变外显子区域的CgGN异构体（CgGN-α、β和γ）。CgGN在闭壳肌和性腺区域的表达随季节变化，在闭壳肌中表达最高。CgGN的自糖基化可与糖原合酶（CgGS）相互作用以完成糖原合成。亚细胞定位分析表明，CgGN异构体和CgGS位于细胞质中。此外，定点诱变实验表明，Tyr200Phe和Tyr202Phe突变会影响CgGN的自糖基化。这是首次对海洋双壳贝类中糖原素功能进行的研究。这些发现将增进我们对软体动物糖原合成和积累机制的理解。这些数据可能有助于培育高糖原牡蛎。
