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Chapter 16

Chapter 16. Hemal Biochemistry. The biochemistry and molecular biology department of CMU. Composition of the blood The liquid element: plasma The formed elements: red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes).

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Chapter 16

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  1. Chapter 16 Hemal Biochemistry The biochemistry and molecular biology department of CMU

  2. Composition of the blood • The liquid element: plasma • The formed elements: red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes). • Plasma --- The blood fraction obtained after removal of the cellular components. • Serum --- The liquid element obtained by allowing the blood to clot.

  3. §1 Heme Synthesis

  4. Sites: Mitochondria and cytoplasm Precursors: Glycine, succinyl CoA, Fe2+

  5. 1. Synthetic pathway of heme (1) The formation of -aminolevulinic acid (ALA) HSCoA + CO2 + ALA synthase (pyridoxal phosphate) In the mitochondria

  6. (2) The formation of porphobilinogen (PBG) ALA dehydratase 2H2O In the cytosol

  7. (3) The formation of uroporphyrinogen Ⅲ (UPGⅢ) and coproporphyrinogen Ⅲ (CPGⅢ) Linear tetrapyrrol Deaminase 4× Porphobilinogen UPG Ⅲ isomerase UPGⅢ decarboxylase CPGⅢ UPGⅢ In the cytosol

  8. (4) The formation of heme CPGⅢ oxidase CPGⅢ Protoporphyrinogen Ⅸ Protopor- phyrinogen Ⅸ oxidase ferrochelatase Protoporphyrin Ⅸ Heme In the mitochondria

  9. PBG Heme Gly succinyl CoA Linear tetrapyrrol Protoporphyrin Ⅸ Protoporphyrinogen Ⅸ CPGⅢ UPGⅢ

  10. 2. Regulation of heme biosynthesis • (1) ALA synthase • Rate-limiting enzyme • Feedback-inhibition by heme • Intensity inhibition by Ferriheme • Inducing by some drugs and hormones (eg. testosterone)

  11. (2) ALA dehydrase and ferrochelatase Inhibited by heme, and heavy metals. (3) Erythropoietin (EPO) can increase synthesis of heme and hemoglobins.

  12. §2Metabolism of Bile Pigment and Jaundice

  13. bile pigment is the main catabolic product of iron porphyrin compound in the body, consisting of bilirubin, biliverdin, bilinogen and bilin.

  14. 1. Formation and transport of bilirubin • ＊The source of bilirubin • The compounds involving iron prophyrin in the body are hemoglobin, myoglobin, cytochrome, peroxidase, and catalase, etc.

  15. ＊Formation of bilirubin • site • In the microsome and cytosol of monokaryon- macrophage system of the liver, spleen, and bone marrow.

  16. process

  17. property • hydrophobic The spatal structure of bilirubin

  18. ＊Transport of Bilirubin • Form of Transport • Bilirubin-albumin complex

  19. 2. Bilirubin conversion in liver ＊ Uptake ＊ Transport Combine with ligandin Smooth Endoplasmic reticulum

  20. ＊ Conjugation bilirubin UDPGA UDP UDP-glucuronyl transferase Bilirubin monoglucuronide UDPGA UDP-glucuronyl transferase UDP Bilirubin diglucuronide

  21. structure of bilirubin diglucuronide

  22. ＊ Excretion Conjugated bilirubin is secreted into the bile and then excreted into the intestine.

  23. 3. Metabolism bilirubin in the intestine Conjugated bilirubin ＊process coliform Free bilirubin Glucuronic acid reduced oxidized bilinogen Bilin

  24. Bilinogen enterohepatic circulation In the terminal ileum and large intestine, a small fraction of the urobilinogens is reabsorbed and reexcreted through the liver to constitute the enterohepatic cycle of urobilinogen.

  25. 4. Serum bilirubin and jaundice • ＊ Serum bilirubin • 1～16mol/l (0.1 ～1mg/dl) • Conjugated bilirubin is also called direct reacting bilirubin or hepatobilirubin. • Free bilirubin is also called indirect reacting bilirubin or hemobilirubin.

  26. difference of two bilirubins

  27. Jaundice • Hemolytic (prehepatic) jaundice • Hepatocellular (hepatic) jaundice • Obstructive (posthepatic) jaundice

  28. Laboratory results in patients with jaundice Hemolytic jaundice Hepatocellular jaundice Obstructive jaundice normal Serum bilirubin < > > > 1 mg/dl 1 mg/dl 1 mg/dl 1 mg/dl total ↑↑ ↑ direct 0~ 0.8mg/dl ↑↑ ↑ < 1 indirect Urine bile pigments – – + + + + urobilirubin ↑ ↓ urobilinogen A few uncertainty ↑ ↓ urobilin A few uncertainty Clay color Simple or normal Color of feces normal dark

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