Commerford S L, Carsten A L, Cronkite E P
Radiat Res. 1983 Apr;94(1):151-5.
The distribution of tritium among the amino acids of serum proteins in mice chronically exposed to tritiated water was determined by ion exchange chromatography of the protein hydrolysate. The specific activity of nonexchangeable tritium in these amino acids relative to the specific activity of tritium in the tissue water of mice ranged from 0.04 for phenylalanine and threonine to 1.0 for glycine and alanine. Since tritium from tissue water can enter the nonexchangeable positions of amino acids only as the result of metabolic processing, the relative specific activity of tritium in each amino acid is an indicator of the extent of such processing. The tritium content of tyrosine and all the amino acids required in the diet for survival is quite low, except for histidine, and can be entirely accounted for by transamination or, in the case of methionine, by transmethylation. The tritium content of the other amino acids is too high to result from such minor processing and must reflect primarily the fraction synthesized de novo. The implications of these findings with respect to the radiobiological consequences of a diet containing tritiated proteins are discussed.
通过对蛋白质水解产物进行离子交换色谱分析，确定了长期暴露于氚化水中的小鼠血清蛋白氨基酸中的氚分布情况。这些氨基酸中不可交换氚的比活相对于小鼠组织水中氚的比活，苯丙氨酸和苏氨酸为0.04，甘氨酸和丙氨酸为1.0。由于组织水中的氚只有经过代谢处理才能进入氨基酸的不可交换位置，因此每个氨基酸中氚的相对比活是这种处理程度的一个指标。酪氨酸以及饮食中生存所需的所有氨基酸的氚含量都相当低，组氨酸除外，并且可以完全由转氨作用来解释，就蛋氨酸而言，则由转甲基作用来解释。其他氨基酸的氚含量过高，不可能是这种微小处理的结果，而必须主要反映从头合成的部分。讨论了这些发现对于含有氚化蛋白质的饮食的放射生物学后果的意义。
