Chang Y F, Adams E
J Bacteriol. 1974 Feb;117(2):753-64. doi: 10.1128/jb.117.2.753-764.1974.
The isolation of several mutant strains blocked in l-lysine degradation has permitted an assessment of the physiological significance of enzymatic reactions related to lysine metabolism in Pseudomonas putida. Additional studies with intact cells involved labeling of metabolic intermediates from radioactive l- or d-lysine, and patterns of enzyme induction in both wild-type and mutant strains. These studies lead to the conclusions that from l-lysine, the obligatory pathway is via delta-aminovaleramide, delta-aminovalerate, glutaric semialdehyde, and glutarate, and that no alternative pathways from l-lysine exist in our strain. A distinct pathway from d-lysine proceeds via Delta(1)-piperideine-2-carboxylate, l-pipecolate, and Delta(1)-piperideine-6-carboxylate (alpha-aminoadipic semialdehyde). The two pathways are independent in the sense that certain mutants, unable to grow on l-lysine, grow at wild-type rates of d-lysine, utilizing the same intermediates as the wild type, as inferred from labeling studies. This finding implies that lysine racemase in our strain, while detectable in cell extracts, is not physiologically functional in intact cells at a rate that would permit growth of mutants blocked in the l-lysine pathway. Pipecolate oxidase, a d-lysine-related enzyme, is induced by d-lysine and less efficiently by l-lysine. Aminooxyacetate virtually abolishes the inducing activity of l-lysine for this enzyme, suggesting that lysine racemase, although functionally inactive for growth purposes, may still have regulatory significance in permitting cross-induction of d-lysine-related enzymes by l-lysine, and vice versa. This finding suggests a mechanism in bacteria for maintaining regulatory patterns in pathways that may have lost their capacity to support growth. In addition, enzymatic studies are reported which implicate Delta(1)-piperideine-2-carboxylate reductase as an early step in the d-lysine pathway.
几种在L-赖氨酸降解过程中受阻的突变菌株的分离，使得人们能够评估与恶臭假单胞菌中赖氨酸代谢相关的酶促反应的生理意义。对完整细胞进行的其他研究包括用放射性L-或D-赖氨酸标记代谢中间体，以及野生型和突变菌株中的酶诱导模式。这些研究得出以下结论：从L-赖氨酸开始，必经途径是通过δ-氨基戊酰胺、δ-氨基戊酸、戊二醛半醛和戊二酸，并且在我们的菌株中不存在L-赖氨酸的替代途径。一条与D-赖氨酸不同的途径是通过Δ(1)-哌啶-2-羧酸、L-哌啶酸和Δ(1)-哌啶-6-羧酸（α-氨基己二酸半醛）。从标记研究推断，这两条途径是独立的，因为某些不能在L-赖氨酸上生长的突变体，能以野生型的速率在D-赖氨酸上生长，利用与野生型相同的中间体。这一发现意味着我们菌株中的赖氨酸消旋酶，虽然在细胞提取物中可检测到，但在完整细胞中其生理功能不足以支持在L-赖氨酸途径中受阻的突变体生长。哌啶酸氧化酶是一种与D-赖氨酸相关的酶，由D-赖氨酸诱导，由L-赖氨酸诱导的效率较低。氨基氧乙酸实际上消除了L-赖氨酸对该酶的诱导活性，这表明赖氨酸消旋酶虽然在功能上对生长无活性，但在允许L-赖氨酸对D-赖氨酸相关酶进行交叉诱导以及反之亦然方面，可能仍具有调节意义。这一发现提示了细菌中一种机制，用于维持可能已丧失支持生长能力的途径中的调节模式。此外，还报道了酶学研究，表明Δ(1)-哌啶-2-羧酸还原酶是D-赖氨酸途径中的早期步骤。
