Zello G A, Pencharz P B, Ball R O
Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada.
Am J Physiol. 1990 Dec;259(6 Pt 1):E835-43. doi: 10.1152/ajpendo.1990.259.6.E835.
Phenylalanine metabolism was determined in 41 studies of adult males (n = 10) consuming an energy-sufficient diet and receiving graded levels of dietary phenylalanine and excess tyrosine (40 mg.kg-1.day-1). After a dietary adaptation period to either 4.2 or 14.0 mg.kg-1.day-1 of phenylalanine; flux, plasma concentration, oxidation, and conversion to tyrosine were measured at test phenylalanine intakes of 5, 7, 10, 14, 21, 28, or 60 mg.kg-1.day-1. Oxidation was low and constant (1.3 mumol.kg-1.h-1) at intakes at or below 10 mg.kg-1.day-1 and increased linearly above this level. Conversion to tyrosine was minimal (2.1%) at these intakes. Breakpoint analysis showed the phenylalanine requirement with excess tyrosine to be 9.1 mg.kg-1.day-1. Plasma phenylalanine concentrations confirmed this estimate of requirement. Prior adaptation did not significantly affect overall flux, plasma concentration, or oxidation nor did it affect the requirement estimate. With the assumption that tyrosine can supply two-thirds of the aromatic amino acid requirement, these data suggest that the aromatic amino acid requirement should be 30 mg.kg-1.day-1 and the World Health Organization recommendation of 14 mg.kg-1.day-1 is an underestimate.
在41项针对成年男性（n = 10）的研究中测定了苯丙氨酸代谢情况，这些男性食用能量充足的饮食，并摄入分级水平的膳食苯丙氨酸和过量酪氨酸（40毫克·千克⁻¹·天⁻¹）。在对4.2或14.0毫克·千克⁻¹·天⁻¹的苯丙氨酸进行饮食适应期后，在测试苯丙氨酸摄入量为5、7、10、14、21、28或60毫克·千克⁻¹·天⁻¹时测量通量、血浆浓度、氧化以及向酪氨酸的转化。在摄入量为10毫克·千克⁻¹·天⁻¹及以下时，氧化率较低且恒定（1.3微摩尔·千克⁻¹·小时⁻¹），高于此水平时呈线性增加。在这些摄入量下，向酪氨酸的转化率最低（2.1%）。断点分析表明，在有过量酪氨酸的情况下，苯丙氨酸需求量为9.1毫克·千克⁻¹·天⁻¹。血浆苯丙氨酸浓度证实了这一需求估计。先前的适应对总体通量、血浆浓度或氧化均无显著影响，也未影响需求估计。假设酪氨酸可满足三分之二的芳香族氨基酸需求，这些数据表明芳香族氨基酸需求量应为30毫克·千克⁻¹·天⁻¹，而世界卫生组织推荐的14毫克·千克⁻¹·天⁻¹被低估了。
