39. Pentose Phosphate Pathway Flashcards
pentose phosphate pathway also known as
texose monophosphate shunt
what is pentose phosphate pathway used for
- produces NADPH
- produces ribose -5- phosphate-> nucleotides
- provides mechanism for use of 5-carbon sugars
what is the substrate of pentose phosphate pathway
glucose -6- phosphate
where does pentose phosphate pathway happen
- RBC
- liver
- adipose
- adrenals
- thyroid
- testes
- lactating mammaries
•cytosol
important products of pentose phosphate pathway
NADPH
ribose-5-phosphate
rate limiting step of pentose phosphate pathway
Glucose-6-phosphate -> 6-phosphogluconate
oxidative, irreversible phase of PPP
first phase
non-oxidative , reversible phase of PPP
second phase
key enzymes of PPP
first phase: glucose-6- phosphate dehydrogenas
second: transketolases
cofactor: thiamine
product of first phase of PPP
2 NADPH
ribulose-5-phosphate
product of second phase of PPP
ribose-5-phosphate
fructose-6-phosphate
glyceraldehyde-3-phosphate
other carbs
- used for reductive biosynthesis of FA and steroids
- gluthathione reduction inside TBCs
- synthesis of Nitric oxidfe
- oxyge dependent bactericidal mechanisms of WBCs
NADPH
gluthathione (G-SH) removes H2O2 in a reaction catalyzed by
gluthathione peroxidase
reduced gluthathione is generated by
gluthathione reductase
requires NADPH
most common disease producing enzyme abnormality in humans
glucose-6- phosphate dehydrogenase deficiency
pathology of G6PD deficiency
- dec NADPH in RBCs
- dec activity of gluthathione reductase
- free radicals and peroxides accumulate
oxidative stress -> hemolytic anemia
precipitating factors of G6PD deficiency
- infection – most common
- drugs (sulfonamides, primaquine, choramphenicol)
- fava beans
altered Hgb that precipitates within RBCs
•Heinz bodies
abnormally shaped RBCs due to phagocytic removal fo heinz bodies in spleen
Bite cells
deficiency in NADPH oxidase
•results in severe, persistent, chronic pyogenic infections caused by catalase-positive bacteria
Chronic granulomatous disease
this converts molecule oxygen into superoxide in leukocytes (neutrophils, macrophages)
and used in the respiratory burst that kills bacteria
NADPH oxidase