Csonka L N
J Biol Chem. 1977 May 25;252(10):3392-8.
3H and 14C tracing data concerning amino acid biosynthetic pathways in Escherichia coli K12 are presented. Thirteen acidic and neutral amino acids were isolated from protein hydrolysates of wild type E. coli K12 grown aerobically or anaerobically in the presence of [U-14C]glucose together with [1-3H]glucose, [3-3H]glucose, [4-3H]glucose, or [6-3H]glucose. The observed 3H/14C counts of the amino acids were compared with the ratios expected on the basis of the input substrate specific activities and present understanding of biosynthetic pathways. For nine amino acids, serine, valine, leucine, threonine, isoleucine, glycine, glutamate, proline, and phenylalanine, the agreement between anticipated and observed specific activities was satisfactory. For the remaining four, methionine, alanine, aspartate, and (in cells labeled with [3-3H]glucose) tyrosine, the anticipated and observed specific activities differed markedly. For alanine, aspartate, and tyrosine, the differences are probably due to exchange of tritium in the course of biosynthesis; for methionine, it may be that there is a principle source of the methyl group other than carbon 3 of serine.
本文给出了关于大肠杆菌K12中氨基酸生物合成途径的3H和14C示踪数据。从在[U-14C]葡萄糖与[1-3H]葡萄糖、[3-3H]葡萄糖、[4-3H]葡萄糖或[6-3H]葡萄糖存在下好氧或厌氧生长的野生型大肠杆菌K12的蛋白质水解物中分离出13种酸性和中性氨基酸。将观察到的氨基酸的3H/14C计数与基于输入底物比活度和目前对生物合成途径的理解所预期的比率进行比较。对于9种氨基酸，丝氨酸、缬氨酸、亮氨酸、苏氨酸、异亮氨酸、甘氨酸、谷氨酸、脯氨酸和苯丙氨酸而言，预期比活度与观察到的比活度之间的一致性令人满意。对于其余4种氨基酸，甲硫氨酸、丙氨酸、天冬氨酸以及（在用[3-3H]葡萄糖标记的细胞中的）酪氨酸，预期比活度与观察到的比活度明显不同。对于丙氨酸、天冬氨酸和酪氨酸，差异可能是由于生物合成过程中氚的交换；对于甲硫氨酸，可能除了丝氨酸的碳3之外，还有甲基的主要来源。
