Cometabolism

Co-metabolism is defined as the simultaneous degradation of two compounds, in which the degradation of the second compound (the secondary substrate) depends on the presence of the first compound (the primary substrate). For example, in the process of metabolizing methane, propane or simple sugars, some bacteria, such as Pseudomonas stutzeri OX1, can degrade hazardous chlorinated solvents, such as tetrachloroethylene and trichloroethylene, that they would otherwise be unable to attack. They do this by producing the methane monooxygenase, enzyme which is known to degrade some pollutants, such as chlorinated solvents, via co-metabolism. Co-metabolism is thus used as an approach to biological degradation of hazardous solvents.

Another example is Mycobacterium vaccae, which uses an enzyme to oxidize propane. Accidentally, this enzyme also oxidizes, at no additional cost for M. vaccae, cyclohexane into cyclohexanol. Thus, cyclohexane is co-metabolized in the presence of propane. This allows for the commensal growth of Pseudomonas on cyclohexane. The latter can metabolize cyclohexanol, but not cyclohexane.^[1]

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1. ^ Beam and Perry (1974)
2. ^ Ryoo, D., Shim, H., Canada, K., Barbieri, P., Wood T. K. (2000) Aerobic Degradation of Tetrachloroethylene by Toluene-o-xylene Monooxoygenase of Pseudomonas Stutzeri OX1, Nat Biotechnol, 18: 775-778.