Zhou M M, Wu Y M, Liu H Y, Liu J X
Institute of Dairy Science, Ministry of Education Key Laboratory of Molecular Animal Nutrition, Zhejiang University, Hangzhou, China; Weifang University of Science and Technology, Shouguang, China.
J Anim Physiol Anim Nutr (Berl). 2015 Apr;99(2):215-20. doi: 10.1111/jpn.12246. Epub 2014 Sep 9.
This study was conducted to investigate the effects of phenylalanine (Phe) and threonine (Thr) oligopeptides on αs1 casein gene expression and milk protein synthesis in bovine mammary epithelial cells. Primary mammary epithelial cells were obtained from Holstein dairy cows and incubated in Dulbecco's modified Eagle's medium-F12 medium (DMEM/F12) containing lactogenic hormones (prolactin and glucocorticoids). Free Phe (117 μg/ml) was substituted partly with peptide-bound Phe (phenylalanylphenylalanine, phenylalanyl threonine, threonyl-phenylalanyl-phenylalanine) in the experimental media. After incubation with experimental medium, cells were collected for gene expression analysis and medium was collected for milk protein or amino acid determination. The results showed that peptide-bound Phe at 10% (11.7 μg/ml) significantly enhanced αs1 casein gene expression and milk protein synthesis as compared with equivalent amount of free Phe. When 10% Phe was replaced by phenylalanylphenylalanine, the disappearance of most essential amino acids increased significantly, and gene expression of peptide transporter 2 and some amino acid transporters was significantly enhanced. These results indicate that the Phe and Thr oligopeptides are important for milk protein synthesis, and peptide-bound amino acids could be utilised more efficiently in milk protein synthesis than the equivalent amount of free amino acids.
本研究旨在探讨苯丙氨酸（Phe）和苏氨酸（Thr）寡肽对牛乳腺上皮细胞中αs1酪蛋白基因表达及乳蛋白合成的影响。从荷斯坦奶牛获取原代乳腺上皮细胞，并在含有泌乳激素（催乳素和糖皮质激素）的杜氏改良伊格尔培养基 - F12培养基（DMEM/F12）中培养。在实验培养基中，游离苯丙氨酸（117μg/ml）部分被肽结合型苯丙氨酸（苯丙氨酰苯丙氨酸、苯丙氨酰苏氨酸、苏氨酰 - 苯丙氨酰 - 苯丙氨酸）替代。用实验培养基孵育后，收集细胞用于基因表达分析，收集培养基用于乳蛋白或氨基酸测定。结果表明，与等量游离苯丙氨酸相比，10%（11.7μg/ml）的肽结合型苯丙氨酸显著增强了αs1酪蛋白基因表达和乳蛋白合成。当10%的苯丙氨酸被苯丙氨酰苯丙氨酸替代时，大多数必需氨基酸的消失显著增加，肽转运体2和一些氨基酸转运体的基因表达显著增强。这些结果表明，苯丙氨酸和苏氨酸寡肽对乳蛋白合成很重要，并且肽结合型氨基酸在乳蛋白合成中比等量游离氨基酸能更有效地被利用。
