Erythrocyte and Heme Biochemistry - Zaidi Flashcards
RBC live how long
120 days
most HB is made where
in the Normoblast before it ejects its nucleus and becomes a Reticulocyte
Fetal Hb
Adult Hb
F : ag
A : aB and ad
Fe on the porphyrin does what when O2 binds
conformational change to line up with heme done on proximal F8 histidine or Hb + globin chain
distal histidine increases affinity for O2 = cooperativity
Myoglobin curve
Hemoglobin curve
Hyperbolic
Sigmoid = Cooperativity
what makes Hb curve sigmoid
cooperativitry and binding affinity of O2 to Hb (66% delivery)
paO2 of exerse and at rest
E: 20 (21% delivery)
R : 40 (+ 45% delivery)
2,3 -BPG does what to Hb curve pH does what to Hb curve CO2 does what to Hb curve H+ does what to Hb curve Histidine does what to Hb curve
lower O2 affinity (left shift) lower O2 affinity Lower O2 affinity Lower O2 affinity Lower O2 affinity
reason H+ releases more O2
protons stabilize Hb so it can release O2 more easilty
reason HbF has higher affinity to O2
it does not respond to 2,3- BPG as well
Sickle Cell anemia
B-globin mutation (Glutamic acid –> Valine)
= research try to make HbF in these people (hydroxyurea right now causes inflammation)
Where is Fe stored
liver, BM, Spleen, GI
Ferritin
binds to Fe+3
Hemosiderin
broken down ferritin
how is Fe absorbed from animal products
- Fe+2 absorbed into Enterocyte
- Fe+2 —-> Fe+3 (Ferroxidase cerruloplasm) (TO BE STORED in ferritin)
- Fe+2 absorbed into blood by Ferroportin
- Fe+2 —-> Fe+3 (Ferroxidase in blood) + bound to transferrin
how is Fe absorbed from non-animal products
- Fe+3 —-> Fe+2 (Duodenal Cytocrome B, Dcytb)
- Fe+2 absorbed into enterocyte (DMT1)
- Fe+2 absorbed into blood by Ferroportin
- Fe+2 —-> Fe+3 (Ferroxidase in blood) + bound to transferrin
Ferroportin needs what to function
Hephaestin
Ferroportin is degraded by what
Hepcidin
what does duodenal cyt b need to function
VIT C
how is Transferrin taken up by target tissue that need Fe
Transferrin binds to TfR
it i internalized
LOW pH = release of Transferrin from TfR
Mito takes FE and makes heme (DMT1)**
what causes Hepcidin to be made
- Transferrin
- TfR
- HFE (Human homeostatic iron regulator protein
what does iron deficiency cause
Tx:
Hypochromic microcytic anemia, pale (low Hb) small RBCs
(aspirn overuse, X absorption, X Fe in diet, GI lood loss)
Fe supplements
what does iron overload cause
causes
TX:
Hereditary Hemochromatosis (HH) Fe can accumulate in heart, liver and pancreas 1. MUTATED HFE 2. upregulated absorption Blood letting + Fe chelators
what 2 things are important for making RBCs
VIT B12 (cobalamin)
FOLATE
= both make DNA
VIT B12 of folate deficiency causes what
Megaloblastic macrocytic anemia (big and normal color (normal Hb levels) RBCs)
= shown in blood smear, BM and has hype-segmented N)
Folate metabolism involves what steps
- Folate
- Dihydrofolate (DHF) = DHF reductase
3, THF = DHF reductase **active form
what is THF truly activated
+ function
what it is methylated (methylyne THF = N5-methyl-THF)
= synthesis of purines (Formyl THF) + T (methylyne THF)
= other DNA synthesis roles
Folic acid in what foods
liver, eggs, milk, legumes, yeast, leafy veggies, citrus fruit
Folic Acid is absorbed where and how long it
SI jejunum
3-6 months in liver
how is THF unmethylated
by VIT B12
Methotrexate
Antineoplastic agent
inhibit DHT reductase = X DNA synthesis in RBCs
= for treating cancer patients
VIT B12 deficiency causes what to happen
Folate is stuck as N5-methyl- THF (folate trap)
megoloblastic macrocytic anemia
vit b 12 reaction on folate
N5-methyl- THF —-> B12-CH3 (methyl cobalamin) + THF
most causes of Vit b 12 deficiency
X IF = pernicious anemia
how is VIT B12 absorbed
- VitB12 + protien R go to duodenum
- Parietal cells make IF that go to duodenum
- Pancrease make protease that degrades Protein R
- IF binds to VitB12 and go to ileum
- IF-VitB12 in blood carried by transcobalamin 2
how to test for VIT B12 deficiency
GOLD standard = Schilling Test
1. see if labeled B12 is in urine (then it is absorbed, if present = low B12 in diet)
2. if no, see if labeled b12 is in urine when IF is added
(then IF deficiency)
Heme structure
porphirin ring with Fe+3 in the middle (4 of them are in Hb)
what type of Fe is in activated Heme
Fe+2 , ferrous
Biosynthesis of Heme happens where
- Mitochondria
- Cytosol
- Mitochondria
Phase 1 Heme synthesis
- Glycine + Succinyl CoA —-> ALA (ALA synthase)
what does ALA synthase need to function
VIT B6
Part 2 of heme synthesis
ALA go into ctoplasm
- 2 ALA —-> Porphobilinogen (PBG) by ALA Dehydrogenase **
- Hydroxymethylbilane (PBG deaminase)
- Uro-porphyrinogen 3 (UP 3 synthase)
- Coprophorynogen 3 (UP 3 decarboxylase)
Part 3 of heme synthesis
Coprophorynogen 3 goes to mito
- CP 3 —-> Protoprophyrinogen 4 (CP 3oxidase)
- PPP 4 —-> Protoporphyrin 4 (PPP 4 oxidase)
- PP 4 —-> HEME ** ( Ferrochelatase)
- feedback in heme synthesis
HEME and Hemin —-I ALA synthase
Lead poisoning caused by
—-I ALA dehydrogenase (ALA buildup)
—-I Ferrochelatase (PP4 buildup)
= ALA resembles GABA, neurotoxic
= microcytic + Hypochromic anemia
Porphyrias are what
acute hepatic :
Erythropoietic :
enzyme in making heme X
neuro sx
skin and photosensitive sx
Acute intermittent porphyria
Hepatic
X PBG deaminase (PBG —-> Hydroxymethylbilane)
Congenital Erythropoietic Porphyria
Erythropoietic
X UP 3 synthase (Hydroxymethylbilane —-> UP 3)
Porythyria Cutanea Tarda
H and E
X UP 3 decarboxylase (UP3 —-> CP3)
Variegate Porphyria
H
X PPP 4 oxidase (PPP4 —-> PP4)
Congenital Erythropoietic Porphyria SX
build up of Uropophyrinogen 1 (UPP1) —-> uroporphyrin 1 (UP1)
= red urine, teeth, photosensitivity
Variegate Porphyria SX
“celebrity porphyrias of King George 3)
= Hallucinate , ABD pain, Convulsions, Delirium
Hb degradation to what
Globin and Heme
Heme degradation
- cleave bridge = Biliverdin (HEME OXYGENASE + O2) **
2. Biliverdin —-> Bilirubin (Biliverdin Reductase)
what is released by heme oxygenase
CO take by Hb
needs O2 to function
Fe+2 —-> Fe +3
how is bilirubin conjugated
- Bilirubin (insoluable) released in BV) + bound to albumin
- BR-albumin is taken to liver
- UDP glucouronyltransferase ** RLS**used to conjugate
- conjugated bilirubin is soluble and goes to gallbladder
UDP glucouronyltransferase
RLS for BR conjugation
2 Glucocuronates + Bilirubin
Conjugated BR becomes what it GI—-> feces and Kindey—-> pee
GI : urobilinogen —-> Stercobilin
Kidney: Urobilin
jaundice is caused by
elevated BR
Pre-Hepatic jaundice
high UC-BR
= hemolytic anemia
= mom-fetus blood incompatibilty
= internal hemorrhage
Intra-Hepatic jaundice
liver problem to conjugate or uptake BR
= Criggler-Najjar Syndrome
= Gilbert Syndrome
Pre-Hepatic jaundice
X BR excretion by bile duct HIGH C-BR (found in urine DARK and stool PALE)**** = Chelstatic jaundice , cholestasis =gall stones = drugs
Criggler-Najjar Syndrome
Type 1
Type 2
X UDP - GT
1 : complete loss
2. mutated so some works
= brain damage
Criggler-Najjar Syndrome Tx
—-I heme oxygenase
phototherapy
eat Ca and carbonate
liver transplant
Gilbert Syndrome
lowered UDP - GT from stress or alcohol or fasting
Hepatitis
inflammed liver
from virus, cirrhosis, or cancer
HIGH C-BR, UC-BR (skin and sclera yellow)
Dark urine
bruise color
Red : heme
green : biliverdin
orange : bilirubin
brown : hemosiderin
Neonatal Jaundice
normal due to HIGH UC-BR (X or low UDP- GT (usually during HbF breakdown)
TX:
1. phototherapy (blue florescent light) = conjugated BR
2. strong —-I heme oxygenase (no heme breakdown)