七烯甲萘醌作为维生素K2的重要亚型,在细胞中主要存在于细胞膜上,在氧化磷酸化的过程中起到电子载体的作用。作为七烯甲萘醌合成过程中的关键酶,1,4-二羟基-2-萘甲酸异戊二烯基转移酶(1,4-dihydroxy-2-naphthoic acid prenyltransferase, MenA)和甲基转移酶(methyltransferase,MenH)目前研究较少,其在细胞中的分布还未被研究,这也限制了七烯甲萘醌产量的进一步提高。该研究重点关注MenA和MenH在细胞内的分布问题,首先构建MenA、MenH和eGFP的融合蛋白,利用荧光定位的方法确定MenA和MenH在细胞中的定位。然后,使用表面活性剂Triton-100破坏细胞膜的结构,发现随着表面活性剂浓度的增加,七烯甲萘醌的合成受到明显抑制。该研究表明细胞膜结构的完整性是七烯甲萘醌合成的前提条件,并且揭示了七烯甲萘醌是在细胞膜上直接被合成,不是被转运到细胞膜中。研究结果为深入探索七烯甲萘醌合成机制提供了方向。
As an important subtype of the fat-soluble vitamin K2, menaquinone-7 (MK-7) plays an important role in the prevention of cardiovascular sclerosis and the treatment of osteoporosis, due to the advantages of long half-life and high biological affinity in human body. Thus, MK-7 has attracted much attention in the fields of medicine and functional food. While studies have shown that MK-7 is a component of the cell membrane and acts as an electron carrier in electron transport, there were few reports on the mechanism of MK-7 entering and leaving the cell membrane. Although 1,4-dihydroxy-2-naphthoic acid prenyl transferase MenA and methyltransferase MenH were known to play an important role in the synthesis of MK-7, there was a lack of in-depth research on their distribution in cells, limiting the further increase in the production of MK-7. We determined the localization of MenA and MenH in cells by fluorescence labeling. Then, the surfactant Triton-100 was used to destroy the cell membrane structure to verify the effect of the integrity of the cell membrane on the synthesis of MK-7. When the concentration of Triton-100 in the fermentation medium was 0.1%, the synthesis of MK-7 was significantly inhibited. When the concentration of Triton-100 reached 0.5%, the synthesis of MK-7 could not be detected. This study reveals that the integrity of cell membrane structure is the prerequisite for the synthesis of MK-7, and MK-7 is synthesized directly on the cell membrane, which is not transported to the cell membrane. The research results provide a direction for in-depth exploration of the synthesis mechanism of menaquinone-7.
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