Steinhardt H J, Adibi S A
Gastroenterology. 1986 Mar;90(3):577-82. doi: 10.1016/0016-5085(86)91111-x.
We have investigated rates of dipeptide disappearance during jejunal perfusion with an equimolar mixture of 12 glycyl-dipeptides and compared amino acid absorption rates from this mixture with those from the corresponding free amino acid mixture in healthy volunteers. All dipeptides contained glycine in the N-terminal position, which was designed to favor peptide absorption rather than hydrolysis. At 2 mM concentration there was little difference in disappearance among dipeptides, but at 6 mM there was some selectivity: Gly-Phe and Gly-Met exhibited the fastest, and Gly-Arg and Gly-His the slowest rates of disappearance. However, between these ends of the spectrum there were only modest differences in disappearance among dipeptides (Gly-Ala, Gly-Thr, Gly-Leu, Gly-Ile, Gly-Val, Gly-Lys, Gly-Pro, Gly-Trp). The amino acid absorption rates were generally smaller but more selective from the free amino acid than from the dipeptide mixture. We conclude that (a) the C-terminal amino acid residue influences intestinal assimilation of glycyl-dipeptides and (b) the considerably greater absorption rate of amino acids from the dipeptide than from the amino acid mixture appears to be the result of uptake by a system that has a greater transport capacity than amino acid carrier systems, thus minimizing competition among its substrates.
我们研究了在健康志愿者中，用12种甘氨酰二肽的等摩尔混合物进行空肠灌注时二肽的消失率，并将该混合物中氨基酸的吸收速率与相应游离氨基酸混合物的吸收速率进行了比较。所有二肽的N端均含有甘氨酸，这旨在促进肽的吸收而非水解。在2 mM浓度下，二肽之间的消失率差异不大，但在6 mM时存在一定的选择性：甘氨酰苯丙氨酸（Gly-Phe）和甘氨酰甲硫氨酸（Gly-Met）的消失速率最快，而甘氨酰精氨酸（Gly-Arg）和甘氨酰组氨酸（Gly-His）的消失速率最慢。然而，在这两个极端之间，二肽（甘氨酰丙氨酸、甘氨酰苏氨酸、甘氨酰亮氨酸、甘氨酰异亮氨酸、甘氨酰缬氨酸、甘氨酰赖氨酸、甘氨酰脯氨酸、甘氨酰色氨酸）的消失率仅有适度差异。游离氨基酸混合物中氨基酸的吸收速率通常较小，但选择性更高。我们得出结论：（a）C端氨基酸残基影响甘氨酰二肽的肠道同化作用；（b）二肽混合物中氨基酸的吸收速率比游离氨基酸混合物中氨基酸的吸收速率显著更高，这似乎是由于一个比氨基酸载体系统具有更大转运能力的系统摄取所致，从而使底物之间的竞争最小化。
