Crop Science Department, Oregon State University, Corvallis, Oregon 97331-3002.
Plant Physiol. 1988 Mar;86(3):941-5. doi: 10.1104/pp.86.3.941.
Foliar urea application on barley plants increased leaf urease activity for 5 hours with a peak of 20-fold at 2 hours. To discern the mode of urease induction, urea with or without inhibitors and [(35)S]methionine were incubated with leaf sections for different lengths of time. Urease was extracted, partially purified, electrophoresed, and then quantified by fluorogram. Five urease (U) isozymes were separated by PAGE. U(a) and U(b) might be polymers or complexes that occurred only at the peak of induced activity. U(1) and U(2) appeared at 0.5 and 0.75 hour, respectively, after urea induction, peaked at 2 hours, and persisted only in treated leaves for several additional hours indicating that they are transient inducible forms. U(3) was the constitutive form present in control and treated leaves. Induction with cordycepin or cycloheximide completely prevented urea stimulated activity and nullified the existence of isozymes U(a), U(b), U(1), and U(2). (35)S-U(1), which was labeled in the last hour of induction, appeared on fluorogram 1 hour after induction, peaked at 2 hours, and declined at 3 hours. Results indicated that de novo synthesis of urease is activated by the influx of urea.
叶面喷施尿素可使大麦叶片脲酶活性在 5 小时内增加 20 倍，在 2 小时时达到峰值。为了辨别脲酶诱导的方式，将含或不含抑制剂的尿素和 [(35)S]甲硫氨酸与叶片切片孵育不同时间。提取、部分纯化脲酶，电泳，然后通过荧光图定量。PAGE 分离出 5 种脲酶 (U) 同工酶。U(a) 和 U(b) 可能是聚合物或复合物，仅在诱导活性的峰值时出现。U(1) 和 U(2)分别在尿素诱导后 0.5 和 0.75 小时出现，在 2 小时时达到峰值，并仅在处理叶片中持续数小时，表明它们是短暂诱导的形式。U(3)是对照和处理叶片中存在的组成型形式。用虫草素或环己酰亚胺诱导可完全阻止尿素刺激的活性，并使同工酶 U(a)、U(b)、U(1)和 U(2)的存在无效。在诱导的最后 1 小时标记的 (35)S-U(1)，在诱导后 1 小时出现在荧光图上，在 2 小时时达到峰值，在 3 小时时下降。结果表明，脲酶的从头合成是由尿素的流入激活的。
