锌的生物学功能、吸收转运及最新研究进展

Research Progress on the Biological Function of Zinc and the Mechanism of Absorption and Transport

锌是机体必需的微量元素，是300多种酶的辅助因子或其组分，在蛋白质和碳水化合物代谢、生长及繁殖中发挥重要作用。锌是血清超氧化物歧化酶的辅助因子，有助于清除机体活性氧分子，锌在上皮细胞、胶原蛋白合成过程中发挥重要作用。日粮zn转换成Zn^2＋并与小肠配体和螯合物结合，经ZIP4-Zn的转运载体跨过刷状缘转运进入肠道上皮细胞。金属硫蛋白可以隔离过量的阳离子（锌）使得组织免受损伤，并通过与锌结合的金属硫蛋白细胞的脱落协助锌使其从粪中排泄。肝脏是锌主要的贮存器官，十二指肠是锌主要的吸收场所。与无机锌比，有机锌具有更强的代谢活性，有机锌的生物学利用率比无机锌高。植酸是很强的二价金属阳离子螯合剂，日粮植酸与锌在pH7.0、锌与植酸的摩尔比为4：1时，植酸与锌有特定的结合力。

Zinc was one of the necessary minerals and it was involved as a cofactor or compo- nent of more than 300 enzymes in the metabolism of protein and carbohydrates, the growth and productivity. Zinc acted as a cofactor of the serum super oxide dismutase which helped to eliminate active oxygen in the body, and zinc played an important role in the synthesis of epithelial cells and collagen. Dietary Zn was converted to Zn^2＋ and bound to ligands and chelates in the small intes- tine to be transported across the brush border into enterocytes by ZIP4, a Zn transporter. Metallo-thionein was to sequester excess cations such as Zn to prevent tissue damage and to aid in the fecal excretion of Zn by the sloughing of ceils containing the MT bound Zn. The liver was the prima- ry storage organ for Zn, and the duodenum was the primary site for Zn absorption. Phytate was a strong chelator of divalent cations, with a preferential binding capacity for Zn, especially at a Zn： phytate molar ratio of 4 ： 1 at pH 7.0.