Post on 17-Jan-2016
description
HMP PATHWAY
HEXOSE MONO PHOSPHATEPATHWAY
INTRODUCTION This pathway is also known as HMP
shunt/pentose phosphate pathway(PP Pathway).
Principal pathway for oxidation of glucose is glycolyis & TCA.
Discovered by Site :In the cytoplasm of all cells except
muscle, and non-lactating mammary gland T(low activity).
OBJECTIVESTo understand the function of
the pentose phosphate pathway in production of NADPH and ribose precursors for nucleic acid synthesis.
To examine the importance of NADPH in protection of cells against highly reactive oxygen species.
To relate defects in the pentose phosphate pathway which can cause disease.
IMPORTANCE OF NADPH
for reductive synthesis of fatty acids,
steroids, amino acids
via glutamate dehydrogena
se & production of
reduced glutathione in erythrocytes
and other cells.
Production of ribose
residues for nucleotide and nucleic
acid synthesis
for H2O2 eliminatio
n from body.
As a energy
molecule.
PP pathway is divided into 2 phase-1. Oxidative phase.
Reactions producing NADPH Irreversible
2.Non-oxidative phase Produces ribose-5-P Reversible reactions feed to glycolysis
Regulatory enzyme
NADPH + H+ is formed from two separate reactions.
The glucose 6-phosphate DH (G6PD) reaction is the rate limiting step and is essentially irreversible.
Cells have a greater need for NADPH than ribose 5-phosphate.
active in liver, adipose tissue, adrenal cortex, thyroid, erythrocytes, testes, and lactating mammary gland.
Transketolase requires the coenzyme thiamine pyrophosphate (TPP), the transaldolase does not.
- not active in non-lactating mammary gland and has low activity in skeletal muscle
Transketolase (TPP) and transaldolase are the link back to glycolysis.Glyceraldehyde 3-phosphateFructose 6-phosphate
Net result:3C5 2C6 + C3
IN THE MUSCLE
HMP Shunt inactive because G 6P Dehydrogenase and 6 P Gluconate Dehydrogenase deficient So they act as checkers for NADPH production.
ribose 5 P synthesized in the way of reverse HMP Shunt or through Transketolase path.
Glucose-6-phosphate dehydrogenase (G6PD)
deficiency causes hemolytic anemia
Mutations present in some populations causes a deficiency in glucose 6-phosphate dehydrogenase, with consequent impairment of NADPH production.
Detoxification of H2O2 is inhibited, and cellular damage results - lipid peroxidation leads to erythrocyte membrane breakdown and hemolytic anemia.
Most G6PD-deficient individuals are asymptomatic - only in combination with certain environmental factors (sulfa antibiotics, herbicides, antimalarials, *divicine) do clinical manifestations occur.
*toxic ingredient of fava beans
Glyceraldehydes 6Phosphate Dehydrogenase(G6PD) deficiency is a X-linked recessive hereditary disease which is due to deficiency Of G6PD,which is req. for RBC metabolism
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