3-Ketoadipate pathway

Canovas JL, RY Stanier (1967) Regulation of the enzymes of the 3-ketoadipate pathway in Moraxella calco-acetica. Eur J Biochem 1 289-300. 

The mandelate pathway in Pseudomonas putida involves successive oxidation to benzoyl formate and benzoate, which is further metabolized via catechol and the 3-ketoadipate pathway (Figure 8.35a) (Hegeman 1966). Both enantiomers of mandelate were degraded through the activity of a mandelate racemase (Hegeman 1966), and the racemase (mdlA) is encoded in an operon that includes the next two enzymes in the pathway—5-mandel-ate dehydrogenase (mdlB) and benzoylformate decarboxylase (mdlC) (Tsou et al. 1990). 

Harwood, C.S. and Parales, R.E. 1996. The (3-ketoadipate pathway and the biology of self-identity. Annu. Rev. Microbiol. 50 553-590. 

Parke D, LN Ornston (1986) Enzymes of the P-ketoadipate pathway are inducible in Rhizobium and Agrobacterium spp. and constitutive in Bradyrhizobium spp. J Bacteriol 165 288-292. 

Robert-Gero M, M Poiret, RY Stanier (1969) The function of the beta-ketoadipate pathway in Pseudomonas acidovorans. J Gen Microbiol 57 207-214. 

Kozarich JW (1988) Enzyme chemistry and evolution in the )S-ketoadipate pathway. In Microbial Metabolism and the Carbon Cycle (Eds SR Hagedorn, RS Hanson, and DA Kunz), pp. 283-302. Harwood Academic Publishers, Chur, Switzerland. 

Stanier, R. Y. Ornston, L.N. (1973). The beta-ketoadipate pathway. Advances in Microbial Physiology, 9, 89-151. 

The mandelate and jS-ketoadipate pathways serve as an example of gene duplication, as there is strong evidence pointing to the former evolving from the latter. Evolution of mandelate racemase from muconate lactonizing enzyme points to the relevance of the enzyme mechanism for catalytic reactivity. 

Example of Gene Duplication Mandelate and a-Ketoadipate Pathways... 

Mandelate racemase (MR) enables some strains of the common soil bacterium Pseudomonas putida to utilize mandelate from decomposing plant matter as a carbon source. MR is the first of five enzymes in the bacterial pathway that converts mandelate to benzoate. Then benzoate is broken down by another set of five enzymes of the ensuing /l-ketoadipate pathway to compounds that can be used to generate ATP, the cell s major source of chemical energy. 

The mandelate and jS-ketoadipate pathways are a good example of gene duplication, with strong evidence of the former evolving from the latter the congruence of MR and MLE, (S)-ManDH and benzoate dihydrodiol dehydrogenase, and possibly benzoyl formate decarboxylase and protocatechuate decarboxylase. 

This -ketoadipate pathway produces e.g., succinic acid, a compound used as monomer for the production of aliphatic polyesters. Already in 1881, the production of e.g., 1,3-propanediol by the fermentation of glycerol was reported [8],... 

Isomerases catalyze conversions within one molecule. For example, the cis.cis-muconate lactonizing enzyme (cycloisomerase) catalyzes the chiral conversion of ds,cis-muconic acid to (K)-muconolactone (Fig. 29). It is a key enz)one in the degradation of benzoate via the p-ketoadipate pathway (109). Chiral lactones could be useful as chiral synthons. 

Classic studies were devoted to the regulation of the enzymes for conversion of catechol and protocatechuate to (l-ketoadipate by Pseudomonas putida (Om-ston 1966), the [f-ketoadipate pathway in Moraxella calcoacetica (Canovas and Stanier 1967), and the mandelate pathway in P. aeruginosa (Rosenberg 1971). All of these organisms cleave the catechol by intradiol fission catalyzed by a... 

The degradation of tryptophan by Pseudomonas fluorescens that takes place via the [1-ketoadipate pathway and by P. acidovorans that utilizes the quinoline pathway (Stanier 1968) ... 

Figure 5. The biocatalytic pathway (boxed arrows) created for microbial conversion of D-glucose into cis, cw-muconate from the perspective of the biochemical pathways from which the enzymes were recruited. Conversion of D-glucose into DHS requires transketolase (tkt) from the pentose phosphate pathway and DAHP synthase (aroF, aroG, aroH)y DHQ synthase aroB and DHQ dehydratase aroD) from the common pathway of aromatic amino acid biosynthesis. Conversion of DHS into catechol requires DHS dehydratase (aroZ, enzyme A) from hydroaromatic catabolism, protocatechuate decarboxylase aroY, enzyme B), and catechol 1,2-dioxygenase (caM, enzyme C) from the benzoate branch of the p-ketoadipate pathway. (Adapted and reproduced with permission from ref. 21.)...

Figure 8.4 Biosynthetic potentiai of Pseudomonas putida. Extended carbon core metabolism of Pseudomonas putida KT2440 including the major catabolic routes of Entner-Doudoroff pathway, Embden-Meyerhof-Parnas pathway, pentose phosphate pathway, tricarboxylic acid cycle, glyoxylate shunt, anaplerotic reactions, fatty acid de novo biosynthesis, p-oxidation of fatty acids, as well as the convergent -ketoadipate pathway for catabolism of aromatics. Known pathways for respective precursor supply for the broad product spectrum of P. putida KT2440 are indicated by light red arrows. Natural products and substrates are highlighted in black, heterologous products and substrates In red.

Figure 3, Converging pathways leading into the fi-ketoadipate pathway, (1), Protocatechuate Branch (2), Catechol Branch. The role ofPobA is shown for clarity.

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