CbiZ, an amidohydrolase enzyme required for salvaging the coenzyme B12 precursor cobinamide in archaea.
CbiZ, an amidohydrolase enzyme required for salvaging the coenzyme B12 precursor cobinamide in archaea.
复制标题
DOI：
10.1073/pnas.0305939101
复制
发表时间：
2004-03
影响因子：
11.1
通讯作者：
J. Woodson;J. Escalante‐Semerena
中科院分区：
文献类型：
--
作者：
J. Woodson;J. Escalante‐Semerena
通过遗传学和生物化学手段，建立了从环境中回收辅酶B（12）前体二氰基辅酶酰胺（Cbi）的途径。该途径需要先前未鉴定的酰胺水解酶的功能，该酶将腺苷二酰胺转化为腺苷二酸，腺苷二酸是从头辅酶B（12）生物合成途径的真正中间体。克隆了产甲烷古菌Methanosarcina mazei菌株Göl的cbiZ基因，在大肠杆菌中过量生产，并将重组蛋白分离至均一。HPLC、UV-可见光谱、MS和生物测定数据确定腺苷酸为CbiZ催化反应的类可啉产物。在极端嗜盐古菌盐杆菌属菌株NRC-1中cbiZ基因的失活阻断了该古菌挽救Cbi的能力。cbiZ功能恢复了肠道沙门氏菌菌株中的Cbi补救，该菌株的Cbi补救途径被阻断。通过CbiZ酶拯救Cbi似乎是古细菌的策略，因为所有产生B（12）的古细菌的基因组都有一个cbiZ直系同源物。两个不同的途径CBI抢救原核生物的进化原因进行了讨论。
The existence of a pathway for salvaging the coenzyme B(12) precursor dicyanocobinamide (Cbi) from the environment was established by genetic and biochemical means. The pathway requires the function of a previously unidentified amidohydrolase enzyme that converts adenosylcobinamide to adenosylcobyric acid, a bona fide intermediate of the de novo coenzyme B(12) biosynthetic route. The cbiZ gene of the methanogenic archaeon Methanosarcina mazei strain Göl was cloned, was overproduced in Escherichia coli, and the recombinant protein was isolated to homogeneity. HPLC, UV-visible spectroscopy, MS, and bioassay data established adenosylcobyric as the corrinoid product of the CbiZ-catalyzed reaction. Inactivation of the cbiZ gene in the extremely halophilic archaeon Halobacterium sp. strain NRC-1 blocked the ability of this archaeon to salvage Cbi. cbiZ function restored Cbi salvaging in a strain of the bacterium Salmonella enterica, whose Cbi-salvaging pathway was blocked. The salvaging of Cbi through the CbiZ enzyme appears to be an archaeal strategy because all of the genomes of B(12)-producing archaea have a cbiZ ortholog. Reasons for the evolution of two distinct pathways for Cbi salvaging in prokaryotes are discussed.