Mechanisms of Genetic Influences on Metabolism

Metabolism is a complex and fascinating process. It is extremely useful in getting rid of bodily toxicants. Apart from all of the toxicants in the man-made environment around us, even animal and plant food contains many chemicals that have no nutritional value but do have potential toxicity. If these chemicals are sufficiently lipid-soluble, they will reach the blood, and they will not be readily excreted unless they are converted to more water-soluble metabolites. This may be the reason why all animals have a wide variety of xenobiotic-metabolizing enzymes that convert a wide range of chemical structures to water-soluble metabolites that can be excreted in urine (Mulder, 2006). 

Humans have a high concentration of xenobiotic-metabolizing enzymes in the gut mucosa and in the liver. This arrangement ensures that systemic exposure to potentially toxic chemicals is limited. A high percentage of these may be caught in first-pass metabolism. However, the normally beneficial first-pass metabolism 

Mulder (2006) noted that drug metabolism can be divided into three phases  

The major oxidative drug-metabolizing pathway is catalyzed by cytochrome P450 enzymes (Mulder, 2006). The abbreviation CYP is typically used in this context. More than 60 CYPs have been identified. These are identified by up to four characters (letters or numbers). For example, in the term CYP2A4 4 the letters and numbers indicate the following  

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