小麦叶片内1,5-二磷酸核酮糖羧化酶/加氧酶大亚基由53 000到50 000裂解反应的定位研究

研究了小麦叶片内1，5-二磷酸核酮糖羧化酶／加氧酶（Rubisco，EC 4．1．1．39）大亚基（LSU）由53000裂解为50000的反应。结果显示，成熟叶片的粗提液在pH5．5的条件下反应后能检测到50000的裂解产物，而暗诱导衰老叶片的粗提液在pH7．5的条件下也能发现LSU的这一降解。分别从成熟叶片和衰老叶片中提取叶绿体，以其裂解液为反应体系研究LSU由53000裂解为50000这步反应的细胞器定位。结果显示，衰老叶片中的叶绿体裂解液在pH7．5时反应1h后能检测到50000降解产物，而成熟叶片叶绿体裂解液在pH5．5和pH7．5的条件下反应后均未检测到LSU的50000裂解产物。上述结果表明：衰老叶片中ISU由53000部分裂解为50000的反应定位于叶绿体内，而成熟叶片中LSU由53000裂解为50000的反应可能定位于叶绿体外。

The localization of the degradation of ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit from 53 000 to 50 000 in wheat leaves

A 50 000 fragment of ribulose-1,5-bisphosphate carboxylase/oxygenase(Rubisco,EC 4.1.1.39)large subunit(LSU)was detected in wheat(Triticum aestivum L.'Yangmai 158')leaves.The 50 000 degradation product could be detected in the crude extracts of mature leaves at pH 5.5,and also be detected in the old leaf extracts at pH 7.5.When using chloroplast as research system,the 50 000 fragment of LSU could only be detected in the chloroplast of senescing leaves when the chloroplast was incubated at pH 7.5 for 1 h.So,the degradation of LSU from 53 000 to 50 000 in senescing leaves was located in the chloroplast,and the degradation of LSU from 53 000 to 50 000 in mature leaves was located out of the chloroplast.