What is an Antimetabolite? How does a normal metabolism work, what are the effects of Antimetabolites on human body?
Antimetabolites;are substances that resemble essential metabolites in molecular structure. They compete with metabolites for incorporation into enzyme molecules involved in metabolism and thus block proper metabolism.
The drug methotrexate (right) is an antimetabolite that interferes with the metabolism of folic acid (left). (Source : wikipedia.org)
Normal Metabolism:
Metabolism consists of the chemical reactions that take place in living tissue; metabolites are the individual substances involved in these reactions. Each individual reaction in the vast metabolic scheme is made to take place with the necessary speed by a complex protein molecule called an enzyme. In general, there is a specific enzyme for each different reaction, and one enzyme cannot substitute for another. Any interference with the working of a particular enzyme will slow one of the reactions of the metabolic scheme. This will affect other related reactions, and these, in turn, will affect still others. A single point of interference can therefore produce a serious disturbance of the organism—a metabolic disease.
Most metabolites can be built up by living tissue out of simpler substances in the course of metabolism. A few, however, cannot be built up in the body but must be ingested, ready-made, with food. These are the essential metabolites (essential, that is, in the diet), and the most prominent ones are the various vitamins. When vitamins are in short supply, the enzymes with which they are associated cannot fulfill their functions, and the various vitamin-deficiency diseases result.
Antimetabolic Interference:
Vitamins, generally, are incorporated into the structures of their associated enzymes. However, an enzyme molecule may incorporate an antimetabolite into its own structure in place of a vitamin, since the shape of the antimetabolite is similar to that of the vitamin. Its structural similarity allows the antimetabolite to fit into the enzyme’s molecular surface in a specifically shaped “hole,” which normally holds the vitamin. An enzyme incorporating such an antimetabolite cannot, however, perform its function in the metabolic scheme. It is as though a nearly correct key, which can be fitted into a lock, cannot be made to turn and open the door. Worse still, this key may break off in the lock, making it inoperable—as an antimetabolite may remain combined with an enzyme molecule over a long period of time.
Bacteria and other parasites can be damaged by antimetabolites. The drug sulfanilamide, for instance, is similar in structure to a substance called para-aminobenzoic acid, which forms a part of folic acid, a vitamin. If the sulfanilamide is administered as an antimetabolite, the bacterial cell uses it in place of para-aminobenzoic acid, producing a mock folic acid. Since this product does not fit into the bacterial metabolism, bacterial growth stops. The body’s natural defenses can then easily handle the stymied bacteria, and an infection is conquered.
***This article is for informational purposes only. It is not a doctor warning or recommendation.
