Notes in L6 - Synthesis of Heme

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Published	11/02/2024	Heme is a {{c1::porphyrin}}
Published	11/02/2024	{{c1::Heme}} is the final product of the porphyrin synthetic pathway, and is the most important porphyrin in humans
Published	11/02/2024	Heme is a porphyrin that consists of one {{c1::Fe2+ atom}} in the center of {{c1::protoporphyrin IX}}
Published	11/02/2024	Major sites of heme biosynthesis are the {{c1::liver}} and {{c1::erythrocyte-producing cells of the bone marrow}}
Published	11/02/2024	The heme biosynthesis pathway begins and ends in {{c1::mitochondria}}, while the steps in between occur in the {{c1::cytosol}}
Published	11/02/2024	Step 1 of Heme Biosynthesis:
Published	11/02/2024	In Step 1 of Heme biosynthesis, formation of ALA by ALA Synthase requires {{c1::pyridoxal phosphate}} as a coenzyme
Published	11/02/2024	Step 2 of Heme Biosynthesis:
Published	11/02/2024	Step 3 of Heme Biosynthesis:
Published	11/02/2024	{{c1::Heme}} and {{c1::Hemin}} can inhibit formation of ALA
Published	11/02/2024	How is hemin produced?
Published	11/02/2024	How does Hemin inhibit the formation of ALA?
Published	11/02/2024	Explain how drugs metabolized by P450 (steroids, alcohol, estrogens, barbituates, etc.) cause an increase in ALA Synthase activity?
Published	11/02/2024	Porphyrias are often inherited as {{c1::autosomal dominant disorders}}, but Congenital Erythropoietic Porphyria is inherited as an {{c1::autosomal rec…
Published	11/02/2024	What are the two classifications of Porphyrias?
Published	11/02/2024	Are porphyrias inherited or acquired?
Published	11/02/2024	How is testing for Porphyrias done?
Published	11/02/2024	What are the two most common porphyrias?
Published	11/02/2024	What are congenital erythropoietic porphyria and erythropoietic protoporphyria characterized by in clinical setting?
Published	11/02/2024	Hemin is heme with iron in the {{c1::ferric (Fe3+)}} state
Published	11/02/2024	Porphyria cutanea tarda can be exaccerbated by:{{c1::Sun}} exposure{{c1::Iron}} overload{{c1::Alcohol::substance}}{{c1::Cytochrome p450}} inducers{{c1…
Published	11/02/2024	Acquired porphyria cutanea tarda typically manifests in the {{c1::fourth/fifth}} decade of a patient's life
Published	11/02/2024	Signs/symptoms of porphyria cutanea tarda include:{{c1::red/brown urine::urine}}{{c1::blistering in sun exposed areas::skin}}{{c1::hair growth in sun …
Published	11/02/2024	characteristics of porphyrins (4)
Published	11/02/2024	Only type {{c1::III}} porphyrins are physiologically important in humans
Published	11/02/2024	porphyrinogens are {{c1::porphyrin precursors}}
Published	11/02/2024	the rate-limiting step of heme biosynthesis is the reaction catalyzed by {{c1::ALA synthase}} to form {{c1::δ-aminolevulinic acid (ALA)}}
Published	11/02/2024	hemin causes a decrease in the synthesis of {{c1::the ALA synthase enzyme}}. when less ALA synthase is produced, then {{c1::less active ALA synthase e…
Published	11/02/2024	Drugs metabolized by the heme-containing microsomal cytochrome P450 mono-oxygenase system cause an increase in ALA synthase activity through a process…
Published	11/02/2024	when excess heme/hemin is present, then ALA synthase synthesis is {{c1::decreased/ repressed}}
Published	11/02/2024	when more heme is needed to be incorporated into hemeproteins, the synthesis of ALA synthase is {{c1::activated/stimulated}}
Published	11/02/2024	lead inhibits the formation of {{c1::porphobilinogen}} and {{c1::heme}}
Published	11/02/2024	lead inhibits {{c1::ALA Dehyratase (δ-aminolevulinc acid dehydratase}}, the enzyme that catalyzes formation of {{c1::porphobilinogen (Step 2 of Heme B…
Published	11/02/2024	Lead also inhibits ferrochetalase, the enzyme that {{c1::promotes incorporation of Fe2+ into Protoporphyrin IX}}
Published	11/02/2024	disorders of specific enzymes in the heme biosynthetic pathway are called {{c1::porphyrias}}. each porphyria results in {{c1::an accumulation of inter…
Published	11/02/2024	{{c1::protoporphyrin}} will be increased in the blood of a patient with lead poisoning
Published	11/02/2024	lead poisoning causes:{{c1::elevation in ALA in urine}}{{c1::anemia when lead is very high}}
Published	11/02/2024	what are the 4 factors that can cause anemia in lead poisoning?
Published	11/02/2024	A common feature of all porphyrias is {{c1::a decreased synthesis of heme}}
Published	11/02/2024	Porphyrias are classified as either {{c1::hepatic}} or {{c1::erythropoietic}} depending on {{c1::whether the enzyme deficiency occurs in the RBC precu…
Published	11/02/2024	porphyrias that result in an accumulation of ALA and porphobilinogen have symptoms that may include {{c1::abdominal pain}} and {{c1::neuropsychiatric …
Published	11/02/2024	Individuals with enzyme defects that lead to the accumulation of tetrapyrrole intermediates show {{c1::photosensitivity}}
Published	11/02/2024	the enzyme involved in acute intermittent porphyria is {{c1::porphobilinogen deaminase}}
Published	11/02/2024	the enzyme involved in porphyria cutanea tarda is {{c1::uroporphyrinogen decarboxylase}}
Published	11/02/2024	symptoms that occur with acute intermittent porphyria
Published	11/02/2024	what can de-repress and repress the pathway in porphyrias?
Published	11/02/2024	what are the symptoms of porphyria cutanea tarda (PCT)?
Published	11/02/2024	which intermediate of the heme biosynthesis pathway accumulates in PCT?
Published	11/02/2024	clinical expression of PCT is influenced by?
Published	11/02/2024	symptoms of AIP are often precipitated by use of {{c1::drugs}} that induce the synthesis of {{c1::cytochrome P450 drug oxidation system}}
Published	11/02/2024	Most patients with {{c1::lead poisoning}} have chronic low levels of exposure and no obvious symptoms
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