ABSTRACT
Castellaniella defragrans
is a
Betaproteobacterium
capable of coupling the oxidation of monoterpenes with denitrification. Geraniol dehydrogenase (GeDH) activity was induced during growth with limonene in comparison to growth with acetate. The N-terminal sequence of the purified enzyme directed the cloning of the corresponding open reading frame (ORF), the first bacterial gene for a GeDH (
geoA
, for
ge
raniol
o
xidation pathway). The
C. defragrans
geraniol dehydrogenase is a homodimeric enzyme that affiliates with the zinc-containing benzyl alcohol dehydrogenases in the superfamily of medium-chain-length dehydrogenases/reductases (MDR). The purified enzyme most efficiently catalyzes the oxidation of perillyl alcohol (
k
cat
/
K
m
= 2.02 × 10
6
M
−1
s
−1
), followed by geraniol (
k
cat
/
K
m
= 1.57 × 10
6
M
−1
s
−1
). Apparent
K
m
values of <10 μM are consistent with an
in vivo
toxicity of geraniol above 5 μM. In the genetic vicinity of
geoA
is a putative aldehyde dehydrogenase that was named
geoB
and identified as a highly abundant protein during growth with phellandrene. Extracts of
Escherichia coli
expressing
geoB
demonstrated
in vitro
a geranial dehydrogenase (GaDH) activity. GaDH activity was independent of coenzyme A. The irreversible formation of geranic acid allows for a metabolic flux from β-myrcene via linalool, geraniol, and geranial to geranic acid.
摘要
螯虾
是一种
倍增菌
能够将单萜氧化与反硝化作用结合起来。在
柠檬烯的生长过程中,
香叶醇脱氢酶(GeDH)的活性比在
醋酸的生长过程中更高。通过纯化酶的 N 端序列,克隆出了相应的开放阅读框(ORF),这是第一个细菌 GeDH
基因(geoA)。
geoA
,表示
地
raniol
o
氧化途径)。藻类
香叶醇脱氢酶
香叶醇脱氢酶是一种同源二聚体酶,与中链长脱氢酶/还原酶(MDR)超家族中的含
锌苄醇脱氢酶属于同源二聚体酶。纯化后的酶能最有效地催化过
乙醇(k)的氧化。
k
cat
/
K
m
= 2.02 × 10
6
M
-1
s
-1
),其次是
香叶醇 (
k
cat
/
K
m
= 1.57 × 10
6
M
-1
s
-1
).显
K
m
值为 <10 μM,与
体内
香叶醇的毒性高于 5 μM。在
基因附近的
geoA
基因附近有一个假定的
醛脱氢酶,被命名为
geoB
并在黄柏生长过程中被鉴定为高含量蛋白质。提取
大肠杆菌
表达
geoB
在
体外
香叶醇脱氢酶(GaDH)的活性。
香叶酸的不可逆形成允许从β-
月桂烯经
芳樟醇、
香叶醇和香叶醛到
香叶酸的代谢通量。