ABSTRACT
3-Sulfinopropionyl coenzyme A (3SP-CoA) desulfinase (Acd
DPN7
) is a new desulfinase that catalyzes the sulfur abstraction from 3SP-CoA in the betaproteobacterium
Advenella mimigardefordensis
strain DPN7
T
. During investigation of a Tn
5
::
mob
-induced mutant defective in growth on 3,3′-dithiodipropionate (DTDP) and also 3-sulfinopropionate (3SP), the transposon insertion was mapped to an open reading frame with the highest homology to an acyl-CoA dehydrogenase (Acd) from
Burkholderia phenoliruptrix
strain BR3459a (83% identical and 91% similar amino acids). An
A. mimigardefordensis
Δ
acd
mutant was generated and verified the observed phenotype of the Tn
5
::
mob
-induced mutant. For enzymatic studies, Acd
DPN7
was heterologously expressed in
Escherichia coli
BL21(DE3)/pLysS by using pET23a::
acd
DPN7
. The purified protein is yellow and contains a noncovalently bound flavin adenine dinucleotide (FAD) cofactor, as verified by high-performance liquid chromatography–electrospray ionization mass spectrometry (HPLC-ESI-MS) analyses. Size-exclusion chromatography revealed a native molecular mass of about 173 kDa, indicating a homotetrameric structure (theoretically 179 kDa), which is in accordance with other members of the acyl-CoA dehydrogenase superfamily.
In vitro
assays unequivocally demonstrated that the purified enzyme converted 3SP-CoA into propionyl-CoA and sulfite (SO
3
2−
). Kinetic studies of Acd
DPN7
revealed a
V
max
of 4.19 μmol min
−1
mg
−1
, an apparent
K
m
of 0.013 mM, and a
k
cat
/
K
m
of 240.8 s
−1
mM
−1
for 3SP-CoA. However, Acd
DPN7
is unable to perform a dehydrogenation, which is the usual reaction catalyzed by members of the acyl-CoA dehydrogenase superfamily. Comparison to other known desulfinases showed a comparably high catalytic efficiency of Acd
DPN7
and indicated a novel reaction mechanism. Hence, Acd
DPN7
encodes a new desulfinase based on an acyl-CoA dehydrogenase (EC 1.3.8.x) scaffold. Concomitantly, we identified the gene product that is responsible for the final desulfination step during catabolism of 3,3′-dithiodipropionate (DTDP), a sulfur-containing precursor substrate for biosynthesis of polythioesters.
摘要
3-Sulfinopropionyl coenzyme A (3SP-CoA) desulfinase (Acd
DPN7
)是一种新的脱硫酶,可催化 betaproteobacterium Advenella mimigardefordensis 中的 3SP-CoA 中的硫抽取。
菌株 DPN7
菌株 DPN7
T
.在研究 Tn
5
::
暴徒
-诱导的突变体在 3,3′-二硫代二丙酸盐(DTDP)和 3-亚硫酸丙酸盐(3SP)上生长有缺陷时,转座子插入被映射到一个开放阅读框上,该阅读框与 Burkholderia phenoluptrix 的酰基-CoA 脱氢酶(Acd)具有最高的同源性。
的酰基-CoA 脱氢酶(Acd
菌株 BR3459a 的酰基-CoA 脱氢酶(Acd)同源性最高(83% 相同,91% 相似)。一个
A. mimigardefordensis
Δ
acd
突变体,并验证了所观察到的 Tn
5
::
mob
-诱导突变体。在酶学研究中,Acd
DPN7
在
大肠杆菌
BL21(DE3)/pLysS 中进行异源表达:
acd
DPN7
.经高效液相色谱-电喷雾质谱(HPLC-ESI-MS)分析验证,纯化的蛋白质呈黄色,含有非共价结合的黄素腺嘌呤二核苷酸(FAD)辅助因子。尺寸排阻色谱法显示其原始分子质量约为 173 kDa,表明其具有同型四聚体结构(理论上为 179 kDa),这与酰基-CoA 脱氢酶超家族的其他成员一致。
体外
实验明确证明,纯化的酶将 3SP-CoA 转化为丙酰基-CoA 和亚硫酸盐(SO
3
2-
).Acd
DPN7
的动力学研究表明
V
最大
为 4.19 μmol min
-1
毫克
-1
,表观
K
m
为 0.013 毫摩尔,而
k
cat
/
K
m
的 240.8 秒
-1
毫摩尔
-1
对 3SP-CoA 而言。然而,Acd
DPN7
却无法进行脱氢反应,而这是酰基-CoA 脱氢酶超家族成员通常催化的反应。与其他已知的脱硫酶相比,Acd
DPN7
的催化效率相当高,并显示出一种新的反应机制。因此,Acd
DPN7
编码了一种基于酰基-CoA 脱氢酶(EC 1.3.8.x)支架的新型脱硫酶。同时,我们还发现了负责 3,3′-二硫代二丙酸酯(DTDP)分解过程中最后脱硫步骤的基因产物,DTDP 是生物合成聚硫醚的含硫前体底物。