heme synthesis feedback?

[HTxFrog]

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During heme sythesis does feedback regulation occur by heme regulating ALA synthase or ALA dehydtratase? First Aid and RR biochem disagree on this so I was just wondering if anyone knew off the top of their head

 

[Bacchus]

I believe its ALA Synthase... but I'll look.

 

[Bacchus]

Yeah, it's ALAS2... Dehydratase is inhibited by lead. ALAS1 is constituitive and ALAS2 is an as needed basis and is regulated by [Fe].

·Makes heme primarily for hemoglobin, which has a long half-life, so its response to heme levels is more leisurely than that of ALAS1
·Regulated primarily in response to iron levels
---Iron response elements in 5' UTR regulate translation (like ferritin)
---Heme may regulate synthesis indirectly by regulating acquisition of Fe from its transport protein, transferrin

 

[HTxFrog]

muchas gracias