ABSTRACT
Pseudomonas putida
uses
l
-lysine as the sole carbon and nitrogen source which preferentially requires its metabolism through two parallel pathways. In one of the pathways δ-aminovalerate is the key metabolite, whereas in the other
l
-lysine is racemized to
d
-lysine, and
l
-pipecolate and α-aminoadipate are the key metabolites. All the genes and enzymes involved in the
d
-lysine pathway, except for those involved in the conversion of
d
-lysine into Δ
1
-piperideine-2-carboxylate, have been identified previously (30). In this study we report that the conversion of
d
-lysine into Δ
1
-piperideine-2-carboxylate can be mediated by a
d
-lysine aminotransferase (PP3590) and a
d
-lysine dehydrogenase (PP3596). From a physiological point of view PP3596 plays a major role in the catabolism of
d
-lysine since its inactivation leads to a marked reduction in the growth rate with
l
- or
d
-lysine as the sole carbon and nitrogen source, whereas inactivation of PP3590 leads only to slowed growth. The gene encoding PP3590, called here
amaC
, forms an operon with
dpkA
, the gene encoding the enzyme involved in conversion of Δ
1
-piperideine-2-carboxylate to
l
-pipecolate in the
d
-lysine catabolic pathway. The gene encoding PP3596, called here
amaD
, is the fifth gene in an operon made up of seven open reading frames (ORFs) encoding PP3592 through PP3597. The
dpkA amaC
operon was transcribed divergently from the operon ORF3592 to ORF3597. Both promoters were mapped by primer extension analysis, which showed that the divergent −35 hexamers of these operon promoters were adjacent to each other. Transcription of both operons was induced in response to
l
- or
d
-lysine in the culture medium.
摘要
假单胞菌
使用
l
-赖氨酸作为唯一的碳源和氮源,因此需要通过两条平行途径进行代谢。在其中一条途径中,δ-氨基戊酸是关键的代谢产物,而在另一条途径中,l-赖氨酸是关键的代谢产物。
l
-赖氨酸消旋化为
d
-赖氨酸,以及
l
-哌啶酸和α-氨基己二酸是关键的代谢产物。参与 d -赖氨酸外消旋化的所有基因和酶
d
-赖氨酸途径中的所有基因和酶,除了参与转化 d
d
-赖氨酸转化为 Δ
1
-哌啶-2-羧酸盐的过程外,其他过程均已确定(30)。在这项研究中,我们报告了
d
-赖氨酸转化为 Δ
1
-哌啶-2-羧酸盐的转化可由一个
d
-赖氨酸氨基转移酶(PP3590)和
d
-赖氨酸脱氢酶(PP3596)介导。从生理学的角度来看,PP3596 在 d -赖氨酸的分解代谢中发挥着重要作用。
d
-赖氨酸的分解代谢中起着重要作用,因为它的失活会导致生长速度明显降低。
l
- 或
d
-赖氨酸作为唯一碳源和氮源时,生长速度会明显降低,而 PP3590 失活只会导致生长速度减慢。编码 PP3590 的基因在这里称为
amaC
与
dpkA
形成一个操作子,该基因编码参与Δ1 和Δ2 转化的酶。
1
-哌啶-2-羧酸转化为
l
哌啶-2-甲酸转化为 l
d
-赖氨酸的代谢途径。编码 PP3596 的基因在这里称为
amaD
是由编码 PP3592 至 PP3597 的七个开放阅读框(ORF)组成的操作子中的第五个基因。其
dpkA amaC
操作子 ORF3592 至 ORF3597 的转录分化。通过引物延伸分析绘制了这两个启动子的图谱,结果表明这两个操作子启动子的-35六聚体彼此相邻。这两个操作子的转录都是在以下条件下被诱导的
l
- 或
d
-赖氨酸诱导两个操作子的转录。