Integrative Medical Biochemistry by Michael W. King

Author:Michael W. King
Language: eng
Format: epub
Publisher: McGraw-Hill Education
Published: 2014-08-10T16:00:00+00:00

Iron is inserted into protoporphyrin IX by ferrochelatase.

Defects in enzymes of porphyrin synthesis result in a family of disorders called the porphyrias. The porphyrias can be divided into erythroid and hepatic forms dependent upon the tissue most affected by the deficiency. Common symptoms of the porphyrias are photosensitivity and variable levels of neurological deficit.

The major site of heme utilization is in erythrocytes. Erythrocytes are in continual flux, dying after approximately 120 days in the circulation. The turnover of erythrocytes creates a significant demand for the degradation of the heme in hemoglobin. Heme degradation occurs primarily in the liver and is initiated via the action of heme oxygenase, the only enzyme in the body to produce carbon monoxide.

The by-product of heme catabolism is bilirubin. Bilirubin is insoluble in the aqueous environment so the liver conjugates it to glucuronic acid to increase its solubility. This reaction is catalyzed by bilirubin DP-glucuronyltransferase.

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