ABSTRACT
Paenibacillus
sp. (formerly
Bacillus macerans
) strain JJ-1b is able to grow on 4-hydroxybenzoate (4HB) as a sole source of carbon and energy and is known to degrade 4HB via the protocatechuate (PCA) 2,3-cleavage pathway. However, none of the genes involved in this pathway have been identified. In this study, we identified and characterized the JJ-1b genes for the 4HB catabolic pathway via the PCA 2,3-cleavage pathway, which consisted of
praR
and
praABEGFDCHI
. Based on the enzyme activities of cell extracts of
Escherichia coli
carrying
praI
,
praA
,
praH
,
praB
,
praC
, and
praD
, these genes were found to code for 4HB 3-hydroxylase, PCA 2,3-dioxygenase, 5-carboxy-2-hydroxymuconate-6-semialdehyde decarboxylase, 2-hydroxymuconate-6-semialdehyde dehydrogenase, 4-oxalocrotonate (OCA) tautomerase, and OCA decarboxylase, respectively, which are involved in the conversion of 4HB into 2-hydroxypenta-2,4-dienoate (HPD). The
praE
,
praF
, and
praG
gene products exhibited 45 to 61% amino acid sequence identity to the corresponding enzymes responsible for the catabolism of HPD to pyruvate and acetyl coenzyme A. The deduced amino acid sequence of
praR
showed similarity with those of IclR-type transcriptional regulators. Reverse transcription-PCR analysis revealed that
praABEGFDCHI
constitute an operon, and these genes were expressed during the growth of JJ-1b on 4HB and PCA.
praR-praABEGFDCHI
conferred the ability to grow on 4HB to
E
.
coli
, suggesting that
praEGF
were functional for the conversion of HPD to pyruvate and acetyl coenzyme A. A promoter analysis suggested that
praR
encodes a repressor of the
pra
operon.
摘要
Paenibacillus
sp.
Bacillus macerans
)菌株 JJ-1b 能够以 4-hydroxybenzoate (4HB) 作为唯一的碳和能量来源进行生长,而且已知它能通过原儿茶酸盐 (PCA) 2,3 裂解途径降解 4HB。然而,参与这一途径的基因尚未被确定。在这项研究中,我们鉴定并描述了通过 PCA 2,3 裂解途径分解 4HB 的 JJ-1b 基因,这些基因包括
praR
和
praABEGFDCHI
.根据大肠杆菌细胞提取物的酶活性
大肠杆菌
携带
praI
,
praA
,
praH
,
praB
,
praC
和
praD
发现这些基因编码 4HB 3-羟化酶、PCA 2,3-二氧 化酶、5-羧基-2-羟基琥珀酸-6-半乳糖醛脱羧酶、2-羟基琥珀酸-6-半乳糖醛脱氢酶、4-oxalocrotonate (OCA) tautomerase 和 OCA decarboxylase,它们分别参与将 4HB 转化为 2-hydroxypenta-2,4-dienoate (HPD)。这些
肽
,
praF
和
和
基因产物的氨基酸序列与负责将HPD分解为丙酮酸和乙酰辅酶A的相应酶具有45%至61%的相同性。
praR
的氨基酸序列与 IclR 型转录调节因子的氨基酸序列相似。反转录-PCR分析表明
praABEGFDCHI
构成一个操作子,这些基因在 JJ-1b 在 4HB 和 PCA 上的生长过程中表达。
praR-praABEGFDCHI
将在 4HB 上生长的能力赋予了
E
.
大肠杆菌
表明
启动子分析表明
启动子分析表明,praEGF
praR
的抑制因子。
启动子
操作子的抑制因子。