维生素B6缺乏的大鼠肝脏中天冬氨酸转氨酶无活性形式增加。

Increase of inactive form of aspartate aminotransferase in pyridoxine-deficient rat liver.

作者信息

Kuroda K, Hirose M, Okada M

出版信息

J Biochem. 1982 Oct;92(4):1079-85. doi: 10.1093/oxfordjournals.jbchem.a134023.

DOI:10.1093/oxfordjournals.jbchem.a134023

Abstract

Cytosolic aspartate aminotransferase from rat liver was separated into at least 3 subforms, focused at pH 6.2, 5.9, and 5.7, by isoelectric focusing. Increase of subforms with low pI values was observed in pyridoxine-deficient rat liver. These subforms with low pI values showed low catalytic activities relative to their antigenic activities. The Km values for substrate and optimal pH values of the two main subforms were not significantly different in pyridoxine-deficient and control rat livers. Some conformational change of enzyme in the cytosol of pyridoxine-deficient rat liver was suggested by circular dichroic and fluorescent spectra. The N and C terminals of the enzyme from both pyridoxine-deficient rats and controls were shown to be alanine and glutamine, respectively.

摘要

通过等电聚焦，将大鼠肝脏中的胞质天冬氨酸转氨酶分离成至少3种亚型，其等电点分别为pH 6.2、5.9和5.7。在吡哆醇缺乏的大鼠肝脏中，观察到低pI值亚型的增加。这些低pI值的亚型相对于其抗原活性表现出较低的催化活性。在吡哆醇缺乏和对照大鼠肝脏中，两种主要亚型的底物Km值和最佳pH值没有显著差异。圆二色光谱和荧光光谱表明，吡哆醇缺乏大鼠肝脏胞质中的酶发生了一些构象变化。结果显示，吡哆醇缺乏大鼠和对照大鼠的该酶N端和C端分别为丙氨酸和谷氨酰胺。