AbstractA P‐450cammonooxygenase enzyme system, obtained through separate purification of the three protein subunits, was used as a biocatalyst in the dehalogenation of 1,2‐dibromo‐3‐chloropropane (DBCP). Incubations in a solution containing the reconstituted enzyme system were performed in two oxygen environments, oxygen‐rich (oxygen‐saturated solution) and oxygen‐lean (oxygen concentration reduced to 1 of saturation), and analyzed for hydrocarbon and bromide ion (Br‐) product formation and the kinetics of DBCP decomposition. l‐Bromo‐3‐chloroacetone (BCA) was identified by gas chromatography‐mass spectrometry as a major product of oxygen‐rich incubations, while 3‐chloro‐l‐propene (allyl chloride) was verified as an oxygen‐lean product. The identification of these two products suggests that P‐450camactivity is occurring in two separate mechanisms, oxidative and reductive, which is governed by the availability of oxygen. This suggestion is further supported by differences that were observed in the DBCP decomposition rate, which is an order of magnitude slower under oxygen‐lean conditions, and differences in bromide ion formation, where approximately one Br‐stoichiometric equivalent is released per mole of DBCP lost under oxygen‐rich conditions versus approximately two Br‐ stoichiome
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