Sehgal P P, Naylor A W
Department of Botany, Duke University, Durham, North Carolina.
Plant Physiol. 1966 Apr;41(4):567-72. doi: 10.1104/pp.41.4.567.
Urease from jack bean meal and hydrated seeds has been obtained in 25 to 33% yield with specific activity in the range of 1000 to 1070 units/mg protein. A purification of 100 to 130-fold was achieved from meal and fully soaked seeds. Use of beta-mercaptoethanol and EDTA was found essential to obtain this high yield and purity. Amino acid analysis showed all 18 amino acids commonly found in proteins. Electrophoresis of urease from soaked seeds (specific activity: 1025 units/mg protein) on a starch-gel block showed 2 peaks. Upon ultracentrifugation of urease samples having a low specific activity (less than 25% pure), the major portion of the urease was probably present in a peak having a sedimentation value of 11 to 12. With relatively pure samples (55-100% pure). S values in the range of 18 to 20 and 24 to 26 were obtained. Usually the purest samples of urease tested without any prior storage lacked the 24 to 26 S peak or the higher polymeric forms. The percentage areas under none of the ultracentrifuge peaks corresponded to the percentage purity of the sample analyzed. It is argued that the physical state of urease in the cell when associated with other seed proteins is as yet uncertain. In crude extracts, a portion of urease exists in a 12 S form but so far data on its origin and specific activity in relation to other species of urease are not available.
从刀豆粉和水合种子中获得的脲酶，产率为25%至33%，比活性在1000至1070单位/毫克蛋白质范围内。从豆粉和充分浸泡的种子中实现了100至130倍的纯化。发现使用β-巯基乙醇和乙二胺四乙酸对于获得如此高的产率和纯度至关重要。氨基酸分析显示了蛋白质中常见的所有18种氨基酸。对浸泡种子中的脲酶（比活性：1025单位/毫克蛋白质）进行淀粉凝胶块电泳显示有2个峰。对比活性低（纯度低于25%）的脲酶样品进行超速离心时，脲酶的主要部分可能存在于沉降值为11至12的峰中。对于相对纯的样品（纯度为55 - 100%），获得的S值在18至20和24至26范围内。通常，未经任何预先储存测试的最纯脲酶样品缺乏24至26 S峰或更高的聚合物形式。超速离心峰下的面积百分比与所分析样品的纯度百分比不对应。有人认为，脲酶在细胞中与其他种子蛋白结合时的物理状态尚不确定。在粗提取物中，一部分脲酶以12 S形式存在，但到目前为止，关于其来源以及与其他脲酶种类相关的比活性的数据尚无可用。
