d -Lysine Catabolic Pathway in Pseudomonas putida: Interrelations with l -Lysine Catabolism

Abstract

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 Lor 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 6-aminovaleramide, 6-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 A 1-piperideine-2-carboxylate, L-pipecolate, and A 1-piperideine-6-carboxylate (a-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-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 A1-piperideine-2-carboxylate reductase as an early step in the-lysine pathway. on the use of mutants, have clarified the status of the utilization of Land D-lysine. Both studies, each in somewhat different ways, strongly suggested the existence of two complete pathways in Pseudomonas, one related to 753

Role of Pipecolic Acid in the Biosynthesis of Lysine in Rhodotorula glutinis

“…These results rule out the possible involvement of A'-piperideine-2-carboxylic acid, which is reported to have absorption maximums of 460 and 500 nm after reaction with ninhydrin (7) and an a Mutants were grown in minimal medium supplemented with 10-5 M L-lysine for 96 h. Pipecolic aciddependent reaction mixtures consisted of: cell free preparations, 2 mg of protein; DL-pipecolic acid, 10 yimol; and phosphate buffer to a final volume of 3 ml.…”

L-Pipecolic acid oxidase, a human enzyme essential for the degradation of L-pipecolic acid, is most similar to the monomeric sarcosine oxidases

“…When pipecolic acid, a six-membered-ring compound containing an imino group, is dehydrogenated to ∆"-piperideine-6-carboxylic acid, this reaction (Figure 8, boxed area) replicates the dehydrogenation of sarcosine. In contrast, -amino acid oxidase forms a double bond on the opposite side of the nitrogen in -pipecolic acid, yielding instead ∆"-piperideine-2-carboxylic acid [27]. Similarly, the fructosyl amino acid oxidases that were identified as somewhat similar to both groups of enzymes also oxidize a ketoamine to an aldehyde and an amine.…”

delta1-piperideine-2-carboxylate reductase of Pseudomonas putida

“…The existence of lysine racemase in Pseudomonias (20,23) led early investigators to believe that Dlysine is also degraded through the same pathway after racemization to the L-enantiomer. However, studies reported more recently (11,13,30) have indicated that D-lysine in Pseuidomonas putida is catabolized through a separate route, the "pipecolate pathway," involving a series of reactions containing six-carbon alicyclic intermediates, as follows: D-lysine Alpiperideine-2-carboxylate -L-pipecolate Alpiperideine-6-carboxylate L-o-aminoadipate.…”

“…Despite the presence of lysine racemase, which is detectable in extracts of this organism (13), this metabolic reaction appears to be inadequate to support growth on L-lysine of mutants blocked in enzymes of the L-lysine pathway (13).…”

“…The limited flow of metabolites between the Dlysine and L-lysine pathways, although not physiologically viable, has been shown to be partially responsible for interpathway enzyme induction (11,13).…”