Step I Heme Synthesis?

[Zback]

A buildup of Heme inhibits which enzyme, ALA synthase or ALA dehydratase? I am getting conflicting reports. I had a professor tell me that Heme buildup inhibits ALA synthase and lead poison inhibits ALA dehydratase. In FA it says that heme and lead both inhibit ALA dehydratase. For ref its on pg 348.

 

[vkhullar]

A buildup of Heme inhibits which enzyme, ALA synthase or ALA dehydratase? I am getting conflicting reports. I had a professor tell me that Heme buildup inhibits ALA synthase and lead poison inhibits ALA dehydratase. In FA it says that heme and lead both inhibit ALA dehydratase. For ref its on pg 348.

We learned in school that :

ALA Synthase inhibited by HEME
ALA Dehydratase + Ferrochelatase inhibited by lead


AND First AID says the same on pg 348 about lead inhibiting ALA dehydratase and not synthase.

As for Heme, well it makes sense if you have low heme you will have increase ALA Synthase activity and hence more ALA dehydratase activity.

 

[Zback]

We learned in school that :

ALA Synthase inhibited by HEME
ALA Dehydratase + Ferrochelatase inhibited by lead


AND First AID says the same on pg 348 about lead inhibiting ALA dehydratase and not synthase.

As for Heme, well it makes sense if you have low heme you will have increase ALA Synthase activity and hence more ALA dehydratase activity.

Yeah, I went back over it again, I misread it I guess. I appreciate it. Anyone ever seen anything related to this on the Step before?

 

[knuckles]

Yeah, I went back over it again, I misread it I guess. I appreciate it. Anyone ever seen anything related to this on the Step before?

It's synthase. They corrected the mistake in the official errata.

 

[aashkab]

UWORLD says heme inhibits ALA synthase as well, along with glucose!

 

[Dakayus]

I think I had a question on it. Person has sideroblastic anemia (ala-s prob) what do you give. the other one is inhibited by Pb2+ to a minor extent but ferrochelatase mostly.