Young S N, Sourkes T L
Acta Vitaminol Enzymol. 1975;29(1-6):299-301.
The in vivo assay of tryptophan pyrrolase gives best results when [ring-2-14C] tryptophan is used and rates of labelled CO2 production are measured at short times after the labelled tryptophan injection. Using this technique in conjunction with in vitro measurements, we find that both tryptophan pyrrolase activity and the liver tryptophan concentration are important factors in controlling the rate of tryptophan breakdown by pyrrolase. Tryptophan in the liver has a very high turnover rate, and the enzyme activity and the liver tryptophan concentration interact. Thus a high liver tryptophan increases the enzyme to speed tryptophan breakdown, while a high pyrrolase activity may tend to lower liver tryptophan, thus tending to decrease both the rate of tryptophan catabolism and possibly the enzyme activity.
当使用[环-2-¹⁴C]色氨酸并在注射标记色氨酸后的短时间内测量标记二氧化碳的产生速率时，色氨酸吡咯酶的体内测定能得到最佳结果。将该技术与体外测量相结合，我们发现色氨酸吡咯酶活性和肝脏色氨酸浓度都是控制色氨酸通过吡咯酶分解速率的重要因素。肝脏中的色氨酸周转率非常高，酶活性和肝脏色氨酸浓度相互作用。因此，肝脏中高浓度的色氨酸会增加酶的活性以加速色氨酸分解，而高吡咯酶活性可能会降低肝脏色氨酸浓度，从而趋于降低色氨酸分解代谢速率以及可能降低酶活性。
