hmp shunt Flashcards
1
Q
what is the function of hmp shunt? (2)
A
- generate NADPH
- generate ribose5P for purine nucleotide synthesis
2
Q
what are the pathways of glucose-6-p? (4)
A
- glucose ↔ G6P (glycolysis/gluconeogenesis)
- G6P→ pyruvate (glycolysis)
- G6P ↔ glycogen (glycogen synthesis)
- G6P→ HMP shunt
3
Q
where does HMP shunt occur? (tissues & organelle)
A
- cytoplasm
- active in tissues w high NADPH usage or in rapidly dividing cells requiring ribose-5-P for nucleic acid synthesis
glutathione reduction: RBC
FA synthesis: adipocytes, liver
steroid synthesis: adrenal cortex, gonads
H: hepatic
M: mammary glands
P: periphery of adrenal cortex
4
Q
what is the rate limiting enzyme of HMP shunt?
A
G6PD
5
Q
how is HMP shunt/G6PD regulated?
A
NADPH/NADP ratio: shortage of NADPH (NADPH/NADP ratio is low)→ activates shunt
6
Q
what is G6PD deficency?
A
- X-linked recessive disease (affects mostly males)
- diff G6PD mutations→ range of clinical symptoms (e.g. none to severe hemolytic anemia)
- G6PD deficiency→ lack of NADPH→ can’t maintain reduced glutathione→ oxidative stress in RBC→ hemolysis→ anemia & jaundice & kernicterus
7
Q
what is a potential advantage of G6PD deficiency?
A
- may confer resistance to malaria
- depletes NADPH→ decrease utilization by parasites for survival in RBCs
8
Q
what are the functions of NADPH? (5)
A
- provides reducing power for biosynthesis (e.g. cholesterol synthesis)
- provides reducing power for detoxification (e.g. liver)
- generates ROS (e.g. WBCs) to kill bacteria
- generates Nitric Oxide (bactericidal, vasodilative)
- glutathione reduction (e.g. RBCs): 2GSH→ GSSG to convert H2O2→ H2O