Identification and characterization of a serine racemase in the silkworm Bombyx mori
Identification and characterization of a serine racemase in the silkworm Bombyx mori
复制标题
家蚕丝氨酸消旋酶的鉴定和表征
DOI：
10.1093/jb/mvac026
复制
发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Ito Tomokazu
中科院分区：
文献类型：
--
作者：
Tanaka Yui;Yoshimura Tohru;Hakamata Maho;Saito Chiaki;Sumitani Megumi;Sezutsu Hideki;Hemmi Hisashi;Ito Tomokazu
鳞翅目昆虫蛹中含有高浓度的内源丝氨酸。在家蚕中，d-丝氨酸在幼虫期可以忽略不计，但在蛹期显著增加，达到总游离丝氨酸的50%。然而，d-丝氨酸的生理功能和负责其生产的酶是未知的。在此，我们鉴定了一种新型的5 '-磷酸吡哆醛（PLP）依赖性丝氨酸消旋酶（SR），它催化B中l-丝氨酸到d-丝氨酸的外消旋化。森。这种蚕SR（BmSR）具有N-末端PLP结合结构域，这是同源的哺乳动物SR和C-末端推定的配体结合调节样结构域（ACT样结构域），这是不存在于哺乳动物SR。类似于哺乳动物SR，BmSR催化的外消旋和脱水的丝氨酸异构体。然而，BmSR与哺乳动物SR不同，其对激活哺乳动物SR所需的Mg ~（2+）/Ca ~（2+）和Mg-ATP不敏感，并且具有高丝氨酸脱水活性。在蛹期，SR活性主要在脂肪体中检测到，这与BmSR表达的时间和定位一致。这些结果是阐明d-丝氨酸在鳞翅目昆虫中生理意义的重要的第一步。
The pupae of lepidopterans contain high concentrations of endogenousd-serine. In the silkwormBombyx mori,d-serine is negligible during the larval stage but increases markedly during the pupal stage, reaching 50% of the total free serine. However, the physiological function ofd-serine and the enzyme responsible for its production is unknown. Herein, we identified a new type of pyridoxal 5′-phosphate (PLP)-dependent serine racemase (SR) that catalyses the racemization ofl-serine tod-serine inB. mori. This silkworm SR (BmSR) has an N-terminal PLP-binding domain that is homologous to mammalian SR and a C-terminal putative ligand-binding regulatory-like domain (ACT-like domain) that is absent in mammalian SR. Similar to mammalian SRs, BmSR catalyses the racemization and dehydration of both serine isomers. However, BmSR is different from mammalian SRs as evidenced by its insensitivity to Mg2+/Ca2+and Mg-ATP—which are required for activation of mammalian SRs—and highd-serine dehydration activity. At the pupal stage, the SR activity was predominantly detected in the fat body, which was consistent with the timing and localization ofBmSRexpression. The results are an important first step in elucidating the physiological significance ofd-serine in lepidopterans.