Heme Biosynthesis in Intermittent Acute Porphyria: Decreased Hepatic Conversion of Porphobilinogen to Porphyrins and Increased Delta Aminolevulinic Acid Synthetase Activity
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TLDR
A micro-radio-chemical assay of delta-aminolevulinic acid synthetase, and some of its applications, are described, and this first and rate-controlling enzyme in the biosynthetic pathway is subject to negative feedback regulation by the end product, heme.Abstract:
Hepatic conversion of porphobilinogen to porphyrins was less than 50% of control levels in human subjects with the genetic disease, intermittent acute porphyria. This relative block in heme biosynthesis may be relevant to a concomitant 6- to 10-fold elevation in δ-aminolevulinic acid synthetase activity, since this first and rate-controlling enzyme in the biosynthetic pathway is subject to negative feedback regulation by the end product, heme. A micro-radio-chemical assay of δ-aminolevulinic acid synthetase, and some of its applications, are described.read more
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Enzyme Defects in the Porphyrias and their Relevance to the Biochemical Abnormalities in these Disorders
TL;DR: Defects in enzymes of the heme biosynthesis pathway underlie the biochemical abnormalities which occur in the porphyrias, and questions have arisen as a result of the demonstrations of enzyme defects in tissues of patients with porphyria.
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Occupational lead exposure: Studies in two brothers showing differential susceptibility to lead
Heinz L. Haust,Heinz L. Haust,Henry C. Poon,Henry C. Poon,Martin J. Inwood,Martin J. Inwood,E.K. O'Hea,E.K. O'Hea,D.S.M. Haines,D.S.M. Haines,C.J. Forret,C.J. Forret,D.S. Keys,D.S. Keys +13 more
TL;DR: The differences in findings between the two brothers point to differential susceptibility to lead and illustrate the extent to which symptomatic lead poisoning may mimic biochemical and clinical features of the acute porphyrias.
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Recent advances in the identification of enzyme deficiencies in the porphyrias.
TL;DR: Three types of porphyria result from defects of enzymes that metabolize porphyrins, or unstable haem precursors that are converted non-enzymatically to porphirins within tissues, and are thus associated with photosensitization.