Amino Acid Metabolism II Flashcards
Porphyrins are synthesized from ____ and _____
glycine and Succinyl CoA
The first step in the biosynthesis of porphyrins is the _____ of glycine and saucily CoA to form ______. this reaction is catalyzed by
Condensation, delta-aminolevulinate. delta-aminolevulinate synthase
The pathway of heme synthesis proceeds with ____ molecules of delta-aminolevulinate
8
ALA dehydratase catalyzes
8 delta-amino levulinate + 8H+ ——> 16 H2O + 4 Porphobilinogen
Porphobilinogen deaminase catalyzes
The condensation of 4 porphobilinogen head to tail to form linear tetrapyrrole
4 porphobilinogen ——> Linear tetrapyrrole
Uroporphyrinogen III synthase (and required cosynthase) catalyze
Linear tetrapyrrole —–> Uroporphyrinogen III
In the presence of uroporphyrinogen III synthase (without cosynthase) what reaction is catalyzed
linear terapyrrole ——> Uroporphyrinogen I
Uroporphyrinogen I is a nonphysiological symmetric isomer
Uroporphyrinogen decarboxylase catalyzes
Uroporphyrinogen III —–> Coproporphyringogen III
Acute intermittent porphyria acts is a defect on what enzyme
porphobilinogen deaminase
Congenital erythropoetic prophyria is a defect of what enzyme
Cosynthase
Coproporphyrinogen III undergoes a desaturation and conversion of two of the propionate side chains into vinyl groups to yield
protoporphyrin IX
the chelation of iron to protoporphrin IX produces
Heme
Heme is the prosthetic group of proteins such as
myoglobin hemoglobin catalase peroxidase cytochrome C
The first step in the degradation of heme is
the cleavage of its alpha-methine bridge to form the green pigment Biliverdin (a linear tetrapyrrole)
Heme + 2O2 + NADPH——> CO + H2O + (NADP+) + Fe+ biliverdin
The central methine bridge of biliverdin is reduced by _________ to form what
biliverdin reductase to form bilirubin
Biliverdin reductase catalyzes
The reduction of the central methine bridge of biliverdin to form bilirubin
Biliverdin + NADPH + (H+) —-> Bilirubin + NADP +
bilirubin is extremely _____
lipophilic
Heme degradation products (_____ and _______)are responsible for the color of bruises
Biliverdin and bilirubin
In heme degradation ______ is excreted
the porphin ring system
UDP glucuronyl transferase does what
it makes bilirubin water soluble so it can be excreted in the urine
Direct bilirubin
=conjugated bilirubin
Indirect bilirubin
= unconjugated bilirubin
- is bound to albumin (albumin normally binds to bilirubin so it can be transferred to the liver)
after ______ bilirubin goes into bile and goes out the common bile duct into the intestine
conjugation
______ is a form of bilirubin that is made in the intestines, it then leaks back into the hepatic vein and is excreted in the urin
urobilinogen
