Carbohydrates Metabolism (HMP Shunt) Flashcards
HMP Shunt end product
- NADPH+H
- Ribose
- 2 Fructose - 6 - phosphate
- 1 Glyceraldehyde - 3 -phosphate
HMP Shunt (Pentose phosphate pathway)
- Alternative way for oxidation of glucose without production of energy
- Anabolic pathway that utilizes 6 Carbons of Glucose to generate 5 Carbon sugars and reducing equivalents (NADPH+H)
HMP Shunt site
Cytoplasm of liver adipose tissues, RBCs, adrenal cortex, ovaries, testis, retina, and lactating mammary glands
HMP Shunt will not occur in …
During dry periods and in non-lactating mammary glands
HMP Shunt phases
Oxidative → Irreversible
Non Oxidative → Reversible
HMP Shunt oxidative phase
Glucose - 6 - phosphate → 6-Phophogluconoulactone → 6-Phophogluconate → Ribulose - 5 - phosphate
Ketose substance
Ribulose - 5 - phosphate , Xylulose - 5 - phosphate
Aldose substance
Ribose - 5 - phosphate
Glucose - 6 - phosphate → 6-Phophogluconoulactone
By … , produce …
Dehydrogenase , Mg
NADPH+H
6-Phophogluconoulactone → 6-Phophogluconate
By …
Hydrolase , Mg
6-Phophogluconate → Ribulose - 5 - phosphate
By … , extract …
Dehydrogenase
NADPH+H , CO2
Ribulose - 5 - phosphate can convert to …… , …..
Ribose - 5 - phosphate by isomerase
Xylulose - 5 - phosphate by epimerase
Ribose - 5 - phosphate + Xylulose - 5 - phosphate
Glyceraldehyde - 3 - phosphate + Sedoheptulose 7 - phosphate
By TPP , Trasketolase which transport 2C from Ribose to Xylulose
Glyceraldehyde - 3 - phosphate + Sedoheptulose 7 - phosphate
Fructose - 6 - phosphate + Eryhtrose - 4 phosphate
By transadolase which transport 1C from Sedoheptulose to Glyceraldehyde
Eryhtrose - 4 phosphate + Xylulose - 5 - phosphate
Fructose - 6 - phosphate + Glyceraldehyde - 3 - phosphate
By Trasketolase which transport 1C from Eryhtrose to Xylulose
The key regulatory enzymes in HMP shunt are …
glucose-6-phosphate and 6- Phospho-gluconate dehydrogenase
HMP Shunt activators
Fed state
Glucose high concentration
Insulin
Thyroxine
NADP “Main reason”
HMP Shunt inhibitors
Starvation
Diabetes mellites
High NADPH+H / NADP ration
Functions and metabolic importance of HMP shunt
- It provides a way or glucose oxidation other than glycolysis and Kreb’s cycle
- It can operate to metabolize dietary pentose sugars derived from the digestion of nucleic acids as well as to rearrange the carbon skeletons of dietary carbohydrates into glycolytic/gluconeogenic intermediates
- Production of pentoses
- Production of NADPH+H+
Tissues must satisfy their own requirement or pentoses since ….
dietary pentoses are not utilizable in DNA , RNA and ribose is not a significant constituent of systemic blood
Pentoses are used for
- Nucleic acids, ribose for RNA and deoxyribose for DNA
- Coenzymes synthesis, e.g., NADS FAD, COASH
- Other free nucleotide Coenzymes , e.g., ATP , GTP
- Synthesis or certain vitamins. e.g. , B2, and B12
Importance of NADPH+H+
a) Synthesis of Fatty acids, Cholesterol, and steroids hormones
b) Synthesis of Non-essential a.a glutamate “reversible glutamate dehydrogenase” , tyrosine from phenylalanine
c) Synthesis of Sphingosine and galactolipids
d) Act as coenzyme for cytochrome P450
e) Reduction of reduced glutathione
HMP Shunt other names
Hexose Monophosphate Pathway
Pentose Shunt
PPP
DNA , RNA ribose comes from
HMP Shunt
