Biotransforming enzymes (Drug Biotransformational Systems – Origins and Aims) (Human Drug Metabolism)

John Lennon once said ‘Before Elvis, there was nothing’. Biologically, this could be paraphrased along the lines of ‘Before bacteria, there was nothing’. Bacterial life has existed on this planet for more than 3.5 billion years and it first emerged in a far more hostile environment than that of today. Bacteria would have had to survive above and below the earth whilst exposed to corrosive/reactive chemicals, heat and lack of oxygen. The phenomenal growth and generation rates of bacteria enabled them to evolve their enzyme systems quickly enough to not only survive but prosper in all environmental niches. Cell structures eventually settled around the format we see now, a largely aqueous cytoplasm bounded by a predominantly lipophilic protective membrane. Although the membrane does prevent entry and exit of many potential toxins, it is no barrier to other lipophilic molecules. If these molecules are highly lipophilic, they will passively diffuse into and become trapped in the membrane. If they are slightly less lipophilic, they will pass through it into the organism. So aside from ‘housekeeping , enzyme systems, some enzymatic protection would have been needed against invading molecules from the immediate environment. Among the various molecular threats to the organism would have been the waste products of other bacteria in decaying biomass, as well as various chemicals formed from incomplete combustion. These would have included aromatic hydrocarbons (multiples of the simplest aromatic, benzene) that can enter living systems and accumulate, thus deranging useful enzymatic systems and cellular structures. Enzymes that can detoxify these pollutants such as aromatics are usually termed ‘biotransforming enzymes’.