|MadSci Network: Biochemistry|
Food mutagens, are or can become highly reactive compounds, which, in this case, means that they bind to molecules such as protein, RNA and DNA in the body very easily. This is not a big deal when the binding occurs to proteins or RNA, because these can easily be replaced. If the binding occurs to DNA (this is called adduction) and if the adduct is not removed, the cell, upon dividing will produce the wrong DNA sequence. When a cell divides to produce a "daughter cell" its DNA must be copied exactly so that the daughter cell looks and acts just like its parent. When DNA is adducted, the DNA of the parent cell will not be copied exactly-there will be mistakes. Once a cell divides, the mistake (mutation) becomes permanent in the daughter cell and the daughter cell will pass the mutation on when it divides. The mutation may have several consequences: no effect, death of the cell, or abnormality of the cell. Abnormal cells can go on to cause cancer in some cases. Cooked food mutagens can be formed from carbohydrates, fats, proteins or combinations of these. Carbohydrates by themselves or along with amino acids can form brown products when heated. The brown color is due to polymer formation in the food. These reactions include caramelization and Maillard Browning. Examples of this include the browning of sugar when it is heated (caramelization) and the browning of bread when toasted (Maillard Browning). Some of the polymers formed are mutagens. When fats are burned (for example when fat from a grilling hamburger drips onto hot coals or flame and produces smoke) compounds known as polycyclic aromatic hydrocarbons are formed. The molecules, when eaten, can be "activated" by enzymes in the body, known as Phase I enzymes, to produce a highly reactive molecule that can form DNA adducts. Proteins may react with heat to form compounds known as heterocyclic amines. These, like polycyclic aromatic hydrocarbons, can be activated by Phase I enzymes and form DNA adducts. Because they contain considerable amounts of both fat and protein, grilled hamburgers contain both polycyclic aromatic hydrocarbons and heterocyclic amines. Most of these are on the outer surface of the burger. Lysinoalanine is a highly reactive molecule which can be formed by a number of food processing operations. Generally, it is the cause of protein degradation, but can cause DNA damage if it comes into contact with DNA. I have included the URLs for Web Pages that contain information about carcinogens, including those which are food mutagens and about "bioactivation", the process by which highly reactive molecules are formed by Phase I enzymes. http://dietetics.mcgill.ca/staff/chan/420/lecture11/index.htm http://sis.nlm.nih.gov/toxtutr1/amenu.htm http://sis.nlm.nih.gov/toxtutr2/amenu.htm Hope this helps. If you have any more questions, please let me know. Keith Harris
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