Department of Biology, McMaster University, Hamilton, Ontario, Canada.
Plant Physiol. 1972 Dec;50(6):649-54. doi: 10.1104/pp.50.6.649.
a lag, a period of rapid increase in enzyme activity and finally a period of relatively minor change. Both inductions are sensitive to 6-methylpurine and cycloheximide. Kinetic studies with 6-methylpurine suggest that the half-life of the messenger RNA for nitrate reductase in both sections is about 20 minutes. The rate of decay of nitrate reductase activity induced by transfer to a nitrate-free medium is slower in root tips (t(1/2) = 3 hours) than in mature root sections (t(1/2) = 2 hours). The enzyme from mature root sections is also less stable to mild heat treatments (27 C; 40 C) than the enzyme from root tip sections. The results indicate that factors regulating enzyme turnover show important changes as root cells mature and may be significant in determining steady state levels of the enzyme.
一个延迟期，一个酶活性快速增加的时期，最后是一个相对变化较小的时期。这两种诱导都对 6-甲基嘌呤和环己酰亚胺敏感。用 6-甲基嘌呤进行的动力学研究表明，两种切片中硝酸盐还原酶的信使 RNA 的半衰期约为 20 分钟。转移到无硝酸盐介质中诱导的硝酸盐还原酶活性的衰减速度在根尖端（t(1/2)=3 小时）比在成熟根段（t(1/2)=2 小时）慢。与根尖端切片中的酶相比，成熟根段中的酶对温和的热处理（27°C；40°C）也不太稳定。结果表明，调节酶周转的因素随着根细胞的成熟而发生重要变化，这可能对确定酶的稳态水平具有重要意义。
