Proposed microbial metabolic pathways

Table 19.3 Known and Proposed Microbial Metabolic Pathways at Deep-Sea Hydrothermal Vents and Cold Seeps. 

Table 8.2 Known and proposed microbial metabolic pathways at deep-sea hydrothermal vents and cold seeps... 

The oxidation of the terminal methyl group of PA produced an AA yield of 6% if Debaryomyces pfaffii was used as biocatalyst [117]. Liu and Yi [118] investigated the diterminal oxidation of 1-decene and 1-dodecene by the mutant SD6 from C. tropicalis. Besides other dicarboxylic acids, AA was detected in both product mixtures. Accordingly, the authors proposed the microbial metabolic pathway. 

Purines are metabolized in a series of reactions involving hypoxanthine, xanthine, uric acid, and allantoin as end products that are subsequently excreted in urine. Fig. 3 shows the metabolic pathways for xanthine. Measurement of urinary excretion of purine metabolites, primarily allantoin or, additionally, uric acid, xanthine, and hypoxanthine, has been proposed as a marker for microbial... 

Figure 11 shows the general steps in the biodesulfurization system based on studies of various bacterial species. " Attention has been given to the microbial chemical pathway which can remove sulfur from substituted dibenzothiophenes with alkyl groups that hinder chemical catalysis and that resist removal by hydrodesulfiirization. Monticello recently outlined sulfiir-specific Cx-DBT metabolism via the hydrocarbon-conserving (4S) pathway first proposed by Campbell and Kee Rhee The activity has been observed in many species of bacteria since the first confirmed isolation by Kilbane in 1988 In most cases, the bacteria have been closely related and catalyze the same reaction. 

D. Leipold, G. Wiinsch, M. Schmidt, H.-J. Bart, T. Bley, H. E. Neuhaus, H. Bergmann, E. Richling, K. Muffler, R. Ulber, Bios5mthesis of ursolic acid derivatives by microbial metabolism of ursolic acid with Nocardia sp. strains—Proposal of new biosynthetic pathways, Process Biochem. 2010. 45, 1043-1051. 

Figure 7. Proposed pathways for the metabolism of EPTC by microbial isolate JE1.

If, during the chemical or enzymatic reduction of the nitro group, the nitroso or hydroxylamine metabolites are produced as discrete intermediates, then numerous reactions other than continued reduction to the amine becomes possible. These new reactions include many that can occur under normal physiological conditions which has led biomedical scientists to propose that the toxic actions of nitroaromatic and arylamine compounds are mediated largely by the production of their nitroso and hydroxylamine metabolites. The same fundamental chemical reactions are likely to contribute to microbial toxicity. On the other hand, several microbes appear to have taken advantage of a major reaction available to arylhydroxylamine compounds, and to have developed enzymes to direct hydroxylamine metabolism towards a pathway that can result in mineralization. 

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