Lysine decarboxylase (LDC; EC 4.1.1.18) of Selenomonas ruminantium is a constitutive enzyme and is involved in the synthesis of cadaverine, which is an essential constituent of the peptidoglycan for normal cell growth. We purified the S. ruminantium LDC by an improved method including hydrophobic chromatography and studied the fine characteristics of the enzyme. Kinetic study of LDC showed that S. ruminanitum LDC decarboxylated both L-lysine and L-ornithine with similar Km and the decarboxylase activities towards both substrates were competitively and irreversibly inhibited by DL-α-difluoromethylornithine, which is a specific inhibitor of ornithine decarboxylase (EC 4.1.1.17). We also showed a drastic descent of LDC activity owing to the degradation of LDC at entry into the stationary phase of cell growth.
瘤胃月形单胞菌(Selenomonas ruminantium)的
赖氨酸脱羧酶(LDC;
EC 4.1.1.18)是一种组成型酶,参与
尸胺的合成,
尸胺是肽聚糖正常细胞生长的必要组成部分。我们通过改进的方法纯化了S. ruminantium的LDC,包括疏
水色谱法,并研究了该酶的精细特性。LDC的动力学研究表明,S. ruminantium的LDC对
L-赖氨酸和
L-鸟氨酸具有相似的Km值进行
脱羧反应,并且对这两种底物的
脱羧活性都被DL-α-
二氟甲基鸟氨酸竞争性和不可逆地抑制,后者是
鸟氨酸脱羧酶(
EC 4.1.1.17)的特异性
抑制剂。我们还表明,由于LDC在细胞生长进入稳定期时发生降解,LDC活性急剧下降。