Asymmetric ring structure• Chelation of Iron
Glycine to form δ-Aminolevulinate
Aminolevulinate Synthase in the mitochondrial matrix
(primarily neg. feedback)
1. transport of δ-Aminolevulinate in to mitochondrian is blocked by high heme concentration
2. translation: neg feedback by heme reduces translation of δ-AminolevulinatemRNA
1. transport to cytosol
2. 2 molecules of δ-Aminolevulinate condense to form each porphobilinogen molecule
4 molecules of porphobilinogen condense head to
tail to form a linear tetrapyrrole molecule with
release of one ammonium ion for each methylene
Synthesis of an asymmetric ring
synthase. Note: this enzyme is also
known as Uroporphyrinogen III
form methyl and vinyl side chains,
and alter saturation of ring constituents, finally ending
with protoporphyrin IX. These reactions take place in the
mitochondrion. Finally, ferrous iron, Fe2+is chelated.
carries iron in the blood and Extracellular space
*can carry two Fe3+ ions
1. acute intermittent
2. congenital erythropoietic
(from rxn 3)
Porphobilinogen and δ-
severe abdominal pain
*think maddness of king george the 3rd
(from rxn 4) cosynthase deficiency
Uroporphyrinogen I, a
symmetric ring, is formed in addition to uroporphyrinogen III.
Uroporphyrinogen I has no use, this ring and its metabolites build up,
because they cannot be
Hemoglobin protein components -globin chains
- are hydrolyzed to individual amino acids.
Iron is recycled.
breaks the alpha methene bridge to release Fe2+
Products: Bilverdin, CO, H2O, NADP+
breaks the central methene bridge
Products: NADP+ and bilirubin
(e- donor is NADH)
*occurs in the spleen
Condensation reaction between Succinyl CoA and Glycine to form delta-Aminolevulinate
*does this so that it can travel in bile (makes it hydrophillic)
In an enzyme catalyzed reaction:Concentrations of products at equilibrium are
Free energy difference between products and reactants: this dictates whether a reaction is spontaneous in the forward direction
• Dependent on the final energy difference of the products and reactants, not the path in between. • • Says nothing about the rate of a reaction.
Activation energy is the amount of energy needed to initiate the reaction
This affects the rate of reaction
- Enzymes effect only the rate of reaction, not the equilibrium.
Vmaxin the presence of inhibitor
Inhibitor competes with substrate for the active site. Addition of more substrate can overcome the effect of the inhibitor
Binds to an enzyme that is already bound with a substrate and decreases the eff of the enzyme
*diff from noncomp. Inhb. Bc noncomp binds the enzyme where this one binds the enzyme-substrate complex.
Km = Km app
Km>Km apparent, Vmax >Vmax apparent