Derepression

In biochemistry, a repressor gene inhibits the activity of an operator gene. By inactivating the repressor, the operator gene becomes active again. This effect is called derepression.

Derepression of ALA synthase

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One example is the effect of drugs on the activity of ALA synthase, an enzyme involved in heme-synthesis. When inducing for example phenobarbital, griseofulvin or hydantoins, the activity of ALA synthase will rise. The cause is a production of cytochrome P450-production, induced by the drugs, consuming heme. When the amount of heme in the liver decreases, it no longer act as a repressor for its synthesis. On the contrary, ALA synthase increases which leads to an increase in heme-production.

References

• Pamela C., Ph.D. Champe, Richard A., Ph.D. Harvey, Denise R., Ph.D. Ferrier, (2004). Lippincott's Illustrated Reviews: Biochemistry 319, 3rd edition, Hagerstwon, MD: Lippincott Williams & Wilkins. ISBN 0-7817-2265-9.