Chapter 20 (Pentose Phosphate Pathway) Flashcards
Pentose Phosphate pathway + ATP
Pentose Phophate pathway does not produce ATP
Parts of PPP
1 – Oxidative pathway (Generates NADPH)
2 – Non-Oxidative pathway (Interconversion of sugars)
Where is the Rate Limiting Step in PPP
In the oxidative Pathway
Where is NADPH produces in PPP
NADPH is produced in the Oxidative Reaction
PPP + other Pathways
PPP –> Glycolysis –> TCA –> ETC
Rate Limiting Enzyme in PPP
Glucophopsphate Dehydrogenase
**In the oxidative step
**Serves as control site for oxidative branch of pathway
***Most important regulatory factor = NADP+
Where does PPP occur
Occurs in the cytoplasm– both phases occur in the cytoplasm
Cofactor for Translocase
Vitamin B1
***Vitimin B1 definciey = have an inssue in the non-oxidative path
- Deficeinc ey in B1 –> Leads to problems in RBCs –> Causes Anemia + Hemolatic disease of newborn
Anemia
Have sickle cell (moon shaped cells) rather than circular cells = lose RBCs
Erythose-4-Phosphate
Erthrose site = electrolyte
Fate of GAP in PPP
GAP can go to Glycolysis
***If PFK 1 doesn’t work then PPP can join glycolysis to help make PPP (because it can make GAP and bypass PFK1)
Key product of PPP
NADPH
NADPH
The source of biosynthetic reducing power
What does PPP produce (general)
NADPH + 5 carbon sugars
Purpose of the first phase of PPP
The first phase of the PPP is the oxidative generation of NADPH
- Purpose is to generate NADPH
***First phase (Oxidative phase) makes NADPH
PPP Equation (NET)
Glu-6_P + 2NADP+ + H2O –> Ribulose-5-P + 2NADPH + 2H+ + CO2
Purpose of the second phase of PPP
Non-oxidative interconversion of a variety of Phsphorylated 3,4,5,6, and 7 carbon sugars
- Second phase makes carbon backbone molecules
- Excess 5 Carbon sugars can be converted into the intermediates of the glycolytic pathway
Example – 2nd phase can make GAP (3 Carbons)
Pathways that require NADPH
Overall = Synthesis + Detoxification
Synthesis:
1. Fatty Acid Biosynthesis
2. Cholesterol Biosynthesis
3. Neurotransmitter biosynthesis
4. Nucleotide biosynthesis
5. RBCs
Detoxification:
1. Reduction of Oxidized Glutathione
2. Cytochrome P450 monooxygenases
***NADPH = used in Reductive biosynthesis + protection against oxidative stress
Two forms Glutathione
- Oxidized
- Reduced
Pentose Phosphate Pathway
Glu-6-P –> Ribulose-5-P
- Ribulose5-P –> Xylulose-5-P or Ribose-5-P
***SLIDE 5
NADPH PRODUCTION
2 molecules of NADPH are generated in the conversion of Glucose-6-Phosphate –> Ribulose-5-P
What intiates the Oxidative phase
Glucose-6-P dehydrogenase
***Glucose-6-P dehydrogenase initiates the oxidative phase of the PPP
- INTIATED – by the conversion of Glucose-6-P –> Phosphoglucono lactone
Rate limiting step in PPP
Glucose-6-P –> 6-Phosphoglucono lactone
Glucose-6-P –> Phosphoglucono lactone
1st step of PPP (1st step of oxidattive poahe)
- Initiates PPP
- Rate Limiting step
- Irreversible
- In the process NADP+ is reduced to NADPH
***Enzyme = Glucose-6-P dehydrogenase
Production of NADPH (depth)
- First made in conversion of Glu-6-P to 6PGL
- Second is made in conversion of 6-PGL –> Ribulose-5-P + CO2
***Both made in oxidative phase
Reversibility of Oxidative Phase
All irreversible – all enzymes involoved are irreversible
Oxidative Phase of PPP (depth)
Photosynthetic organisms + NADPH
Photosynthetic organisms use light to generate NADPH
NADPH in all organisms
There is a path present in all organisms to generate NADPH –> helps cells meet NADPH needs in non-photosynthetic organisms + in non-photosynthetic tissues in plant
Use of PPP
PPP = crucial source of NADPH
How much NADPH is produced
2 molecules of NADPH –> done in conversion of Glu-6-P –> Ribulose-5-P
Oxidative Pahe depth
- Start with dehydrogenation of Glu-6-P at C1
- Catylyzed by Glu-6-P dehydrogenase
Glu-6-P –> 6-PGL
- Catylyzed by Glu-6-P dehydrogenase
- 6-PGL is hydrolyzed
- Catylyzed by Lactonase
6-PGL –> 6-Phospho-gluconate
- Catylyzed by Lactonase
- Oxidative decarboxylation of 6-phosphogluconate
- Produces Ribulose-5-P + NADPH
6-Phosphogluconate –> Ribulose-5-P
6-Phosphoglucono Lactone
Intramolecular ester between C1 crabanyl and C5 OH group
6-Phosphogluconate
6 Carbon sugar acid
Link between PPP and Glycolysis
PPP and Glycolysis are linked by Transketolase and Transaldolase
Potential Fates of Ribulose-5-P
- Ribose-5-P
- Xyulose-5-P
Ribulose-5-P –> Ribose-5-P
Ribulose-5-P can be isomerized to Ribose-5-P
***Catylyzed by Phosphopentose isomerase
Where can Ribose-5-P be used
Ribose-5-P and dertaibes of it = used in RNA + DNA + ATP + NADH + FADH2 + CoA
- Ribose-5-P = precurssor for many biomolecules
Making Ribose-5-P vs. NADPH
Ribose-5-P = precurssory for many biomolecules BUT many cells need NADPH for reductive biosyntehsis more than they need Robose-5-P to be encorporated into nucleotides
Example – Adipose Tissue + Liver + Mammary glands = need NADPH for Fatty Acid Synthesis – in this case Ribose-5-P is converted to GAP –> Fru-6P by transketolase and Transaldose
Net result of Transketolase and Transaldolase
Formation of 2 Hexroses + 1 Triose from 3 pentose
3 C5 –> 2 C6 + C3
Overall Reactions in Non-Oxidative Phase
C5 + C5 –> C3 + C7 (Transketolase)
C3 + C7 –> C6 + C4 (Transaldolase)
C4 + C5 –> C6 + C3 (Transketolase)
NET: 3 C5 –> 2 C6 + C3
***ALL REVERSIBLE REACTIONS
Reactions in Non-Oxidative Phase
- Formation of GAP and Sedoheptulose from 2 pentoses
- GAP and sedpheptulose = reaction to from Fru-6-P and Erthrose-4-P
- Ribulose-5-P is converted into Xylulose (epimer of Ribulose)
- Caytylyzed by Phosphopentose epimerase - Tranketolase catylyzes synthesis of Fru-6-P and GAP from Erthrose-4-P and Xylulose-5-P
SUM of Reactions: 2Xylulose-5-P + Ribose-5-P –> 2Fru-6-P + GAP
Formation of GAP and Sedoheptulose
Formed from Xyulose-5-P + Ribose-5-P
Xylose-5-P + Ribose-5-P –> GAP + Sedohetulose-7-P
Overall: 2 five carbon sugares –> converted to a three and sevent carbon sugar
***Catalyzed by Transketolase
THEN – GAP and sedpheptulose = reaction to from Fru-6-P and Erthrose-4-P
Formation of GAP and Sedoheptulose (depth)
Xylulose-5-P = acts as donor of 2 Carbon unit
Substrates for Transketolase
Ketose substartes –
For Formation of GAP and Sedoheptiulose requires – ONLY in OH at C3 with configuration of Xylulose NOT the configuration of Ribulose
Xylulose-5-P
Epimer of Ribulose-5-P
***Substrate for transketolate –> transketolase requires that it is in the confisguation of Xyulose-5-P (C3 OH is in the Xyulose confirmation NOT the Ribulose confirmation)
Ribulose-5-P –> Xylulose-5-P
Flips configuration of OH at C3 –> needed for transketolase to function
***Catylyzed by Phsphopentose epimerase
- Occurs in Calvin Cycle
All enzymes in non-oxidative phase
Are reversible
Fate of GAP and Sedoheptulose-7-P
They react to form Fru-6-P and Erthrose-4-P
***Catylyzed by Transaldolase
- Occurs in calcin Cycle
Transaldolase
C3 + C7 –> C6 + C4
GAP + Sedohetulose-7-P –> Fructose-6-P + Erthrose-4-P
Where is Erythrose-4-P
In RBCs
Transketolase
C4 + C5 –> C6 + C3
Erthose-4-P + Xylulose-5-P –> Fru-6-P + GAP
Fate of Erthose-4-P + Xylulose-5-P
Forms Fru-6-P + GAP
***Caylyzed by Transketolase
Three enzymes in Non-oxidative
- Epimerase
- Transketolase
- Transaldolase
NET non-oxidative pathway
2Xylulose-5-P + Ribose-5-P –> 2Fru-6-P + GAP
***Shows the conversion of 3 C5 into the components of glycolitic and gluconogenic pathways
END NET – NET (of non-oxidative): 3Ribose-5-P –> 2 Fru-6-P + GAP
- net is due to conversion of Robose-5-P –> Xyluose-5-P
Ribose-5P –> Xylulose-5-P
Ribose-5P –> Xylulose-5-P – catylzed by sequuentia actions of:
1. Phosphopentose Isomerase
2. Phsphopentose Epimerase
Makes NET (of non-oxidative): 3Ribose-5-P –> 2 Fru-6-P + GAP
Fate of excess Ribose-5-P
Excess Ribose-5-P in PPP –> can be completley converted to glycolytic intermediates
Ingested Ribose
Any ingested Ribose can be processed to glycolytic intermediates
Conversion of carbon skelotons
Carbon skeletons of sugars can be rearranged to meet physiological needs
Key in Transketolase and Transaldolase mechanisms
Both have a carbanion intermediate – both stabilize anionic intermediate in different ways
Transketolase Mechanism
- Thiamine Pyrophophate (TPP) forms carbanion – C2 of TPP ionizes to give a carbanion
- The carbanion attacks the Ketose Substrate – the negitive charge of Carbon attaches the crabayl of ketose substarte
- A carbon-Carbon bond is cleaves – releases the aldose product + forms TPP joined to a two carbon fragment – the resulting addition compoun relases aldose pructu to yeild an activated Glyceraldgey unit
- 2 Carbon fragment = Glycoaldehyde intermediate
4l. The intermediate attacks the aldose substrate - The positiv charge on Nitrogen in thiazome ring acta a electron sink in develipment of activated intermediate
- The cranyl o faldrose acceptor condenses with activated glyceraldhy init to form a keto
- 2 Carbon fragment = Glycoaldehyde intermediate
- The ketose product is release and TPP is ready for another cycle
***Reversible rxn
Cofactor or Transketolase
TPP – Transketolase = contains a tightly bound TPP
Transketolase (overall mechanism)
Transketolase trasnfers a 2 crabon glyceradlhy from a ketose donor to an aldrose acceptor
***Site of addition of 2 carbon unit is thiazole ring of TPP
***Transketolase = homologous to E1 subunit of Pyrivate Dehydrigenase complex
Transketolase vs. Transaldoase mechanisms
Reactions by both enzymes = similar BUT distict
- Differencse = trasnketolase trasnfers a 2 carbion unit but trasnaldolase transfers a 3 carbon unit
***Each unit transientley attactches to enzyme in reaction –> thus the enzymes are examples of double replacement reactions
Transaldolase reaction (mech overall)
Overall – Transaldoase transfers a 3 carbon dihydroxy acetone unit form ketose donor to aldose acceotor
Prostetic group of Transaldolase
Doesn’t require a prostetic group RATHER a schiff base is formed between the crabanyl of ketose substrate and amino group pf Lysine at Active site of enzyme
What is in active site of Transaldose
A schiff base – formed between the crabanyl of ketose substrate and amino group pf Lysine at Active site of enzyme
***Requires Lysin
Transaldolase Mechanism
- From a chiff base – A schiff base forms between the enzyme and the ketone substate
- Shiff base is protonates –> bond between C3 and C4 is split
- Protonation of the schiff base = results in release of aldose product
- Upon reportinateion – Aldose product is relased = leaves 3 carbon fragment bound to the enzyme
- Negitive charge on shciff base crabaion = stabilized by resonance
- Positive nitrogen atom of protinated shiff = acts as elecrton sink
- release of the asldose product generates a subsituted enzyme intermediap
- Schiff base product is stable unit suitabke aldrose is bound
- the DHA = reacts with carbanyl group of aldole –> protination allows formation of new C-C bond
- The three crabon fragment bound to enzyme adds to the aldose substrate
- Subsequnet deprotination occurs
- Following deprotination –> have hydrolysis of schiff base = release ketose product
Stabilization of Carbanion in both reactions
Stabilized by resonance
N in Schiff base vs Thiozole ring
Nitrogen in Protinated Schiff base (tansaldolase) = plays the same role as Thiozole ring (Transketolase)
- both electon sinks
- In botyh reactinos a group within intermediate reactions like crabanions in attacking the carbanyl to form a C-C bond
Second name for PPP pathway?
HMP
Sites of PPP
- Lactating mammary glands – FA and Steroid Synthesis
- Liver – FA and Steroid Synthesis
- Adrenal Cortex (Above Kidneys) – slows down during puberty
- Red Blood Cells
Puberty + Adrenal Cortex
The Adrenal Cortex slows down during Puberty – the hypothalamus takes over to produce sex hormones
***Hypothalamus doesn’t stop until you die
Adrenal Cortex Location
Adrenal cortex = sits above kidneys
- Adrenal Gland = Outside
- Medula = Inside
Role of medula
Responsible for Epinephrine and Norephinerphine
Adrenal Cortex issues
Get Adrenal Issue if there is chemical envirnment or if you drink alcholol or smoke cogaretttes
- If either the mom of dad smokes or drinks
***Adrenal cortex problems = an issue because get bad RBCs
Glu-6-P dehydrogenase deficiency
Have decrease in NADPH in RBCs = get hemolytic Anemia due to poor RBCs defense against oxidizing agents
- Anmeia –> could lead to need to amputate
- X-linked recessive disease
- Most common human enxyme defciencey
- more common in African American people + people in the far east
- Increase Malaria resistnce because masquitoes don’t like the blood
- Have decrease in NADPH
- Have no oxidative phase = have no non-oxidative phase
Beta-Thalamasssia
More sever version of Anemia
Use of PPP for detoxification
Glu-6-P –> 6-PGL – uses an NAD+ – MEANS you need to regenerate NADP+ for path to continue
To regenrate NAD+ – GSSG –> GSH + GSH – regenerates NADP+ BUT ALSO in the process of reducing GSSH you can Oxidize H2O2 –> 2H2O
(Enzyme = Glutathione reductase)
***Couples the regernation of NADP+ with the oxidation of H2O2 to detoxofy H2O2 and make water
What is the PPP coordinated with?
The PPP is coordinated with Glycolysis – escially regarding Metabolism of Glu-6-P
What controls the rate of the oxidative phase PPP
The rate of the oxidative phase in PPP is controlled by the level of NADP+
***The most important regulatory factor is the concentration of NADP+
***The effect of NADP+ level on the rate of Oxidative phase ensures that NADPH is not being generated unless supply is needed for reduction biosynthesis or protection against oxidative stress has decreased
What controls the flow of Glu-6-P
Need for:
1. NADPH
2. Ribose-5-P
3. ATP (The PPP doesnt require of make ATP BUT it is connected to pathways that do make ATP – conneceted to Glycolysis which does make ATP = ATP concentration affects PPP)
Modes of the PPP
- Ribose-5-P need excess the need for NADPH
- The NADPH and Ribose-5-P needs are balanced
- More NADPH is needed than Ribose-5-P
- NADPH and ATP are both required
Where do the modes of PPP come from?
The PPP can operate in four modes that result from the combinations of the oxidative phase + non-oxidative phase + glycolysis + gluconeogenesis
Situation with Glu-6-P in glycolysios and PPP
Glu-6-P is metabolized by BOTH the PPP and glycolysis –> how is teh porcessing of it partitioned between the two paths?
Answer: The cytoplasmic concentration of NADP+ plays a key role in determining the fate of Glu-6-P
What determines if Glu-6-P will be process via PPP or glycolysis?
The cytoplasmic concentration of NADP+
How does NADP+ affct Glu-6-P dehydrogenase
Decrease in NADP+ = limites Glu-6-P dehydrogenase (limits dehydration) – because NADP+ is needed as electron acceptor
Intensification on levels of NADP+
Decrease in NADP+ is intensified by the fact that NADPH competes with NADP+ for binding to enzyme
When is NADPH needed/produced
NADPH is only generated if the body needs supply for reductive biosynthesis or protection against oxidative stress
***The efefct of using NADP+ levels as the rate determining for oxidative step ensures that NADPH is not being produced unless supply is needed for reductive biosythesis or protection against oxidative stress
What controls the rate of the non-oxidative stage?
The non-oxidative phase is controlled primarily by the avalability of substrates
Mode #1 (depth) – more ribose than NADPH needed
Example – rapidly dividing cells need Robose-5-P for synthesios of nucleotide precurssors of DMA
- Most of the Glu-6-P = converted to Fru-6-P and GAP by glycolysis
- Transaldolase and Tranketolase convert 2 molecules of Fru-6-P and 1 molecule of GAP into 3 molecules of Ribose-5-P
Glycolysis –> THEN TA and TK used Glycolytic intermediates to make Ribose-5-P
MOde #2 (depth) - Need for NADPH and Ribose is the same
Glu-6-P is processed to 1 Ribulose-5-P + 2NADPH
- Ribulose-5-P is converted to Ribose-5-P
Mode #3 (depth) - More NADPH is required than Ribose
Example - Fat tissues = required high NADPH for synthesis of Fatty Acids
Here – Glu-6-P is completeley oxidized to CO2 (Glycolysis + TCA)
Three groups of reactions are active:
1. Oxidative phase of PPP – get 2NADPH + 1Ribulose-5-P
2. Non-oxidative phase (TA + TK) – Ribulose-5-P is converted to Fru-6-P + GAP
3. Glu-6-P is resynthesized from Fru-6-P and GAP made by TA/TK –> THEN the Glu-6-P can be sued to make more NADPH
NET PPP reactions (FIND OUT WHAT THIS IS SUM OF)
Glu-6-P + 12 NADP+ + 7H2O + 6O2 + 12NADPH + 12H + Pi
***Mean equation of Glu-6-P can be comlpetley oxidized for CO2 with gernation of NADPH –> in essence the ribose-5-P producved by PPP is recycled into Glu-6-P by TK and TA and enzymes in gluconogenic path
Mode #4 (depth) – Both NADPH and ATP are required
Ribulose-5-P is produced by PPP –> converted to Pryruvate
- The Fru-6-P and GAP from Robose-5-P enter the glycolytic path –> get ATP
HERE – ATP and NADPH are both generated and 5 of teh 6 carbons of glucose end in Pyrruvate
- Pyruvate generated can be oxidized to generate more ATP OR it can be used for other things
Tissues with Active PPP
- Adrenal Gland – Steroid Synthesis
- Liver –> FA and Steroid Synthesis
- Testes –> Steroid Synthesis
- Adipose Tissue –> FA synthesis
- Ovary –> Steroid Synthesis
- Mammary Gland –> FA Synthesis
- RBCs –> Maintenance of Reduced Glutathione
Issue with taking extra Steroids
Affects the reproductive system
Hypervitaminosis
Too many vitamens - bad
Example – Increase vitamen D = Increase Ca2+ = Hypercalcemia = probelms with muscle + heart
Rapid Cell growth + PPP
The PPP is required for Rapid cell growth
- Rapidly divding cells need Ribose-5-P for Nucleic Acid Synthesis + NADPH for FA and memebrane syntehsis
- The glycolytic intermediates are diverted into PPP
What do rapidly dividing cells need
- Robose-5-P –> for Nucleic Acid Synthesis
- NADPH –> For FA and memebrane synthesis
***All of these can come from PPP –> rapidly dividing cells need PPP
Diversion of Glycolytic intermediates to PPP
DONE in rapidly dividing cells
***Done by expressing Pyruvate Kinase isozyme (PKM) AND by inhibiting the Triosphosphate isomerase by PEP (PEP is a substrate of PKM)
Catalytic Activity of Pyruvate Kinase Isozyme
Low Catalytic Activity –> Makes bottleneck in Glycolytic pathway = glycolytic intermediates accumalate = they are then used in PPP = get NADPH and Ribose-5-p
Rapidly dividing cells + PPP (depth)
Rapidly dividing cells = switch to aerobic glycolysis –> Glu-6-P and glycolitic intermediates are then used to generate NADPH and Ribose-5-P
Rapidly dividing cells + PPP (depth)
Rapidly dividing cells = switch to aerobic glycolysis –> Glu-6-P and glycolitic intermediates are then used to generate NADPH and Ribose-5-P
Key use of Glu-6-P dehydrigenase
Glu-6-P dehydrogenase plays a key role in protection against reactive oxygen species
Glutathione use
Glutathione = helps prevent damage by ROS that are generated in the course of metabolism
GSSH –> 2GSH
GSSH = Oxidized Glutathione
GSH = reduced Glutathione
GSSG –> 2GSH + NADP+
***Uses NADPH to reduce GSSG (GDDG is reduced while NADPH is oxidized)
***NADPH generated in the PPP by Glu-6-P dehydrogenase is required to maintain adequate levels of reduced Glutathione
NADPH + reduced Glutathione
NADPH generated in the PPP by Glu-6-P dehydrogenase is required to maintain adequate levels of reduced Glutathione
Cells with lower levels of Glu-6-P dehydrogenase
Cells with lower levels of Glu-6-P dehydrogenase are sensitive to oxidative stress
AA needed for reduced Glutathione
- Glutamate
- Cysteine
- Glycine
Glu-6-P dehydrogenase deficiency
People with deficiency have hemolysis
**Can occur from consumption of fava beans or fava pollen
**Makes people more sensitive to oxidative stress
Use of GSH
GSH normally helps to control amounts of harmful Peroxides that are released by some agents
***Peroxides = ROS
Reaction – 2GSH + ROOH (Peroxide) –> GSSG + H2O + ROH
- Enzyme = Glutathione Peroxidase
Role of NADPH in RBCs
In RBCs – the main role of NADPH is to regernate the reduced form of GSH
***because RBCs lack Mitochondria
Reaction – GSSG + NADPH –> 2GSH + NADP+
Enzyme = Glutathione Reductase
Glutathione reductase
GSSG + NADPH –> 2GSH + NADP+
Fava Beans
Contain a purine Glycoside that causes oxidative damage to RBCs – indicses hemolysis
- Can lead to Glu-6-P
dehydrogenase deficiency –> Can lead to hemolysis (“favism respoonse”
- Vicine = the pyromidne glycoside in fava beans
***Can get probelm from eating fava beans or from inhaling the pollen
Favism Respnse
When eating fava leads to Glu-6-P dehydrogenase deficinecey = leaves to hemolysis
***More common in African Americans
Hemolysis
Destruction of RBCs
What is glutathione needed for?
Glutathione = needed for hemoglobine – Glutathione is required to maintain the normal sturctire of hemoglobin because it helps maintain the Cysteine residues in their reduced form (bonds to sulfar)
- No gluathione = no RBCs –> Anemia
Low Glutathione
In the absence of Glutathione –> Sulfhydryl bonds occur among the hemoglobin molecules = forms agreggated (Forms Heinze bodies) –> Red blodd cells then Lyse
***Likley due to Glu-6-P dehydrogenase deficiency
Heinz bodies
Agreggates of hemoglobin that form when have low Glutathione
***red dot in image = heinz body
What tissue doesn’t have Nuceli
RBCs – RBCs survive 120 days then the old ones go through Apoptosis
Advantage of Glu-6-P deficiency
Glu-6-P dehydrogenase definciencey = orotects against malaria
How does Glu-6-P dehydrigenase deficiency prtect against malaria
By depriving the parisites of NADPH that they need in order to grow – because the PPP is compromised the cell and parasite die from oxidative damage
What causes malaria
Parasites – the parisites that cause disease need NADPH for growth
Humingbirds + PPP
Active animals that are susceptible to damage by ROS
Humingbirds have a high activinty in PPP (in both stages) –> allows them to use carb nector to produce ATP to power muscle activity – while doing so they can also make NADPH which protects against ROS
Active animals + PPP
All aerobic animals that are highly active face the problem of damage by ROS
***More active = more susceptible to damage by ROS
RQ for organisms that use carbs only as fuel
When organisms are using carbohydrates only as fuel RQ = 1
Calculating RQ
CO2/O2
Humingbirds RQ
When humingbirds us carbs as fuel RQ = >1
***The extra CO2 = comes from the PPP – they have a high activinty in PPP (in both stages) –> allows them to use carb nector to produce ATP to power muscle activity – while doing so they can also make NADPH which protects against ROS
Human Altheletes comsuming carbs during excersize
Human athletes who consume carbohydrates during intense extended excerisize may also use the PPP for ROS protection
Affect of ROS
ROS inflicts damage on all classes of macromolecules + can lead to cell death
- ROS = implicated in a number of human disease (ex. Diabetes)
Reduced Glutathione (deopth)
Tripeptide with a free sulfhydryl group – combats oxidative stress by reducing ROS to harmless forms
WHEN REUDUCING ROS –> the gulathione is oxidized to GSSG – THEN THE GSSG must be reduced to regernate GSH
Pamaquine
First synthetic Anti-malarial drug –> associated with the appearnace of severse and mysterious ailments – a few pateints developed sever symptoms (Black pee + Juandice + Hemglobin content in blood decrease –> in some casses teh destruction of red blood cells causes cell death)
- Drug indiced Hemolytic anemia
Accutness of Glu-6-P dehydrogenase deficiency
More accute in RBCs – because they lack mitocondria = they have no means of generating reducing power
Primaquine
Antimalarial drug closely to pamaquine that is widley used in malaria prone regions of the world
How does pamaquine + Primaquin + fava cause hemolysis?
The chemicals are oxidative reagents that genrate peroxides
- Glu-6-P dehydrigenase is required to maintain glutathion levels in order to protect aginst oxidative stress – RBCs will be lowered is there is less reduced glutathione – and without dehydrgenase the peroxides wil cometinue to damage because no NADPH is being made to ereduce gluathione
Glutathione Peroxidase
2GSH + ROOH –> GSSG + H2O + ROH
***Uses glutathione as a reducing agent to eliminate peroxides
Role of NADPH in RBCS
Reduces the disulfide form of Glutathione to sulfhydryl form using Glutathione reductase
Membranes damaged by heinz bodies
Membranes damaged by heinz bodies and ROS become deformed = the cell explodes
What group has the more Glu-6-P dehydrigenase defciencey
African Americans – high frequencey suffest that the defeciencey mighty be advatgeghous under certain envrinmental conditions
ANSWER: the deficiency helps protect against malaria = it is in higher frequencey in places with malaria in the world
Health conundrum about Glu-6-P dehydrigenase deficiencey
primiquine is commonly used as an efective anti-malarial drug BUT indricriminate use caises hemolysis in people with defeicney
SOLUTION – may to mane an anti-malarial vaccine
