#Biochemistery
#Carbohydrate_metabolism
#بوست_رقم (9)
الليلة ح نتكلم عن
pentose phosphate pathway
ودي النقاط اللي ح اتكلم عنها
📌 Definition.
📌location.
📌 Steps.
📌Functions.
📌Regulation.
📌Defect.
يلا بسم الله نبدأ👋
Pentoses phosphate pathway, Hexose monophosphate shunt (HMP) , phosphogluconate pathway.
🌸 Definition:
It is alternative pathway for glucose oxidation, to produced NADPH, H and Pentoses.
🌸 Location:
Intracellular location: Cytosol
Organ location:
a. In tissues where NADPH, H is needed for fatty acids and steroids synthesis, such as:
1. Adipose tissue and liver: it supplies NADPH, H+ for lipogenesis.
2. Adrenal cortex , ovaries and testes: for steroid synthesis.
3. Red cells: for production of reduced glutathione.
4. Retina.
5. Lactating mammary gland.
b. In many tissues it supplies pentoses for synthesis of nucleotides.
🌸 Steps: this pathway occurs in two phases:
1. Oxidative (irreversible) phase: where 3 molecules of glucose 6-phosphate are converted into 3 molecules of ribulose-5-phosphate with production of NADPH, H+ and CO2.
2. Non-oxidative (reversible) phase: where the 3 molecules of ribulose-5-phosphate are interacted and converted into 2 molecules of glucose-6-phosphate and 1 molecule of glyceraldhyde-3-phosphate.
الكلام والخطوات دي بالتفصيل موضحة في الصورة المرفقة تحت 👇
🌸Functions of PPP:-
1. Production of pentoses which are essential for synthesis of nucleic acids (RNA and DNA), nucleotides (ATP, GTP) and coenzymes (NAD+,FAD).
2. Production of NADPH, H+ it is important for:
1. Synthesis of many substrate:
a. Synthesis of fatty acids ,cholesterol and other steroid hormons.
b. Essential for glucuronic acid metabolism.
C. Synthesis of of sphingosine and galactolipids.
2. In RBCs, reduction of glutathione .
طيب ال reduced glutathione دا مهم في شنو؟ 😉
1. Normal integrity of RBCs.
2. Removal of hydrogen peroxide,which is a toxic compound that causes cell membrane fragility by conversion of hemoglobin into met-hemoglobin (toxic compounds).
3. Detoxication of many drugs and carcinogens.
3. In liver, hydroxylation of toxic aromatic and aliphatic compounds such as steroids,alcohols and many drugs to non toxic compounds.
4. In WBCs, phagocytosis (engulfment) of microorganisms and foreign bodies by WBCs , contain NADPH, H+ oxidase enzyme present in cell membrane.
🍁 طيب بعد تحصل عملية البلعمة دي (phagocytosis) بحصل شنو؟
NADPH+H oxidase converts O2 into superoxide ions.
العملية دي زاتها بتاعت تحول الاوكسجين ل superoxide بسموها respiratory burst .
☘يلا ال superoxide بتحول ل hydrogen peroxide بواسطة superoxide dismutase enzyme .
☘ hydrogen peroxide is converted into hypochlorite (HOCL-) by myeloperoxidase in the presence of HCL, which kills bacteria.
عشان كدا لو حصل deficiency في NADPH+H oxidase ح يؤدي ل chronic bacterial infection
🌸 Regulation of PPP:
كالعادة ال regulation بحصل عن طريق key enzymes وهنا عندي انزيم واحد بس وهو glucose-6-phosphate DH .
It stimulated by: Insulin and NADP+.
Inhibited by: NADPH, H+ and acetyl CoA.
🌸 Defects of PPP:
1. Hemolytic anemia.
2.Favism (Deficiency of glucose-6-phosphate Dehydrogenase):
🍁 Definition:
it is type of hemolytic anemia (excessive destruction of RBCS) after ingestion of fava beans and some other compounds.
These compounds alter the structure of the enzyme —> decrease in G-6-P dehydrogenase activity.
🍁 Mechanism:
Deficiency of G-6-P dehydrogenase —> decrease NADPH, H+ production (which is essential to reduce glutathione in RBCs)
وعرفنا انه ال reduced glutathione بنحتاجه ل remove hydrogen peroxide.
🔥 كدا للفهم بتاع ال favism دا :
Deficiency of G-6-P DH —> decrease NADPH, H+ —> decrease reduced glutathione —> accumlation of hydrogen peroxide —> hemolysis of RBCs.
🍁 Signs and symptoms:
1. Hemolytic anemia.
2. Sever jaundice and decreased hemoglobin concentration when exposed to certain oxidizing agent such as:
1. Special food as: fava beans.
2. Antimalarial drugs as: primaquine.
3. Antibiotics as: streptomycin and sulfa.
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