大肠杆菌生物合成型和生物降解型鸟氨酸脱羧酶的比较。

Comparison of the biosynthetic and biodegradative ornithine decarboxylases of Escherichia coli.

作者信息

Applebaum D M, Dunlap J C, Morris D R

出版信息

Biochemistry. 1977 Apr 19;16(8):1580-4. doi: 10.1021/bi00627a008.

Abstract

Biosynthetic ornithine decarboxylase was purified 4300-fold from Escherichia coli to a purity of approximately 85% as judged by polyacrylamide gel electrophoresis. The enzyme showed hyperbolic kinetics with a Km of 5.6 mM for ornithine and 1.0 micronM for pyridoxal phosphate and it was competitively inhibited by putrescine and spermidine. The biosynthetic decarboxylase was compared with the biodegradative ornithine decarboxylase [Applebaum, D., et al. (1975), Biochemistry 14, 3675]. Both enzymes were dimers of 80 000-82 000 molecular weight and exhibited similar kinetic properties. However, they differed significantly in other respects. The pH optimum of the biosynthetic enzyme was 8.1, compared with 6.9 for the biodegradative. Both enzymes were activated by nucleotides, but with different specificity. Antibody to the purified biodegradative ornithine decarboxylase did not cross-react with the biosynthetic enzyme. The evolutionary relationship of these two decarboxylases to the other amino acid decarboxylases of E. coli is discussed.

摘要

通过聚丙烯酰胺凝胶电泳判断，生物合成的鸟氨酸脱羧酶从大肠杆菌中纯化了4300倍，纯度约为85%。该酶呈现双曲线动力学，对鸟氨酸的Km为5.6 mM，对磷酸吡哆醛的Km为1.0 μM，腐胺和亚精胺对其有竞争性抑制作用。将生物合成脱羧酶与生物降解性鸟氨酸脱羧酶[Applebaum, D.,等人（1975年），《生物化学》14, 3675]进行了比较。两种酶均为分子量80 000 - 82 000的二聚体，且表现出相似的动力学性质。然而，它们在其他方面存在显著差异。生物合成酶的最适pH为8.1，而生物降解性酶的最适pH为6.9。两种酶均被核苷酸激活，但具有不同的特异性。纯化的生物降解性鸟氨酸脱羧酶的抗体与生物合成酶不发生交叉反应。讨论了这两种脱羧酶与大肠杆菌其他氨基酸脱羧酶的进化关系。