Coordinate synthesis of heme and apoenzyme in the formation of tryptophan pyrrolase.

Reciprocal control mechanisms between hemoprotein and 8-aminolevulinic acid synthetase take part in coordinate synthesis of the heme and apoenzyme moieties of tryptophan pyrrolase. Stimulation of heme biosynthesis increases tryptophan pyrrolase, whereas enhancement of heme binding by apotryptophan pyrrolase secondarily increases the formation of delta-aminolevulinic acid synthetase, the rate-limiting enzyme in heme formation. Tryptophan-mediated induction of delta-aminolevulinic acid synthetase suggests that heme participates in repression of that enzyme