嗜冷弧菌ATCase的酶学特性

ENZYMOLOGICAL PROPERTIES OF ATCASE FROM A PSYCHROPHILICVIBRIO 2693

从非洲２８００米深的海底分离的嗜冷弧菌（ｐｓｙｃｈｒｏｐｈｉｌｉｃＶｉｂｒｉｏｓｐ．）菌株２６９３的天冬氨酸氨甲酰基转移酶（ＡＴＣａｓｅ）进行了某些酶学特性方面的研究。该酶由一条催化链和一条调节链组成，全酶的分子量为３５０ｋｕ。酶反应最适温度在３７℃左右。该酶受嘧啶生物合成的最终产物ＣＴＰ的反馈抑制。但是，嘌呤途径的最终产物ＡＴＰ并没有表现出明显的激活作用。

Studies of enzymological properties of ATCase from a psychrophilic Vibrio sp., strain 2693 revealedthat the activity increased gradually with temperature between 0 and 37℃. Above 40℃, the activity decreased. The optimal temperature for thes enzyme was about 37℃. Still considerable activity was observed at 0℃. ATCaseactivity did not appreciably decreased, up to 50℃, but thereafter drastically declined. It can be seen that theenzyme was almost completely inactivated by a 15 min incubation at 60℃. The transtion midpoint was about55℃. This enzyme is feed-back inhibited by CTP, the end product of pyrimidine biosynthesis, however it is notappreciably ectivated by ATP, one end product of the Purine pathway . The ATCase consisted of a catalytic and aregulatory chain, the molecular mass of the holoenzyme approximates 350Ku.