Week 10 - Unit 2 Flashcards
PPP stands for ?
Pentose MonoPhosphate Pathway- alternative oxidative pathway for glucose-6P
What are the two primary roles of PPP?
- Generation of 5-C sugars for nucleotide synthesis
- Generation of NADPH
(essential in red blood cell which does not have mitochondria to fully oxidize glucose)
The generation of ______ within the red blood cell is critical for the maintenance of glutathione in the reduced state.
NADPH
_______ is required to maintain hemoglobin in the reduced form to bind oxygen.
Glutathoine
Deficiencies in the ____ greatly impact red blood cell stability.
PPP
Fructose can come from what 3 sources?
- Dietary fructose (honey)
- Dietary Sucrose (Glucose + fructose)
- Converted from Glucose to Fructose in Polyol pathway
Fructose, like glucose, comes into the cell and is immediately phosphorylated by ?
Fructokinase
- Makes Fructose 1-P
Fructose ——-> Fructose -1P——–>(cleaved by what enzyme into two products?)
Aldolase B
Fructose—–>Fructose-1-P——>cleaved by Aldolase B ———–> (what are the two products?)
- Dihydroxyacetone - P
2. Glyceraldehyde
Aldolase B is active in what organ? how is it different from Aldolase A?
Aldolase B is in liver- used in both fructose and glucose pathway
Aldolase A- in muscle- only in glucose pathway
What does Aldolase B cleave in the Fructose pathway?
in the glucose pathway?
Fructose-1P
Fructose 1,6 Bisphosphate (glycolysis)
After Fructose 1-P is cleaved into Dihydroxyacetone-P and Glyceraldehyde, what must occur next for Glyceraldehyde before it can be used to make Pyruvate?
Glyceraldehyde is already 3-P version in glycolysis , but not in fructose pathway, so it must be phosphorylated by ATP into Glyceraldehyde 3-P
What is the enzyme that phosphorylates Glyceraldehyde in the fructose pathway to make its 3-P version?
Triose Kinase (takes P from ATP to make it ADP)
What is the rate limiting step for Fructose pathway ?
the Aldolase B enzyme (cleavage of Fructose 1-P)
Aldolase B has a much higher affinity for _______ in the Glycolysis pathway from glucose than _______ in fructose pathway.
Fructose 1,6 Bisphosphate
Fructose 1-P (will be much slower reaction)
After ingesting high amounts of fructose , normal individuals will accumulate ______ in the liver while is slowly cleaved by Aldolase B.
Fructose 1-P
Hereditary Fructose Intolerance is what type of genetic disorder?
Autosomal Recessive disorder
What are individuals missing in Hereditary Fructose Intolerance disorder?
Aldolase B
What happens to people with Hereditary Fructose Intolerance when they ingest fructose?
Accumulation of Fructose 1-P in liver (no aldolase B to cleave it)
- impacts ability to regulate blood glucose
- can lead to HYPOGLYCEMIA
- Can cause major clinical problems
What is Essential Fructosuria?
Individuals lack Fructokinase enzyme - can not convert fructose to fructose-1-P inside cells
-few clinical consequences
What happens when someone with Fructosuria ingests fructose?
It is not phosphorylated and metabolized but is rather just excreted in urine (sugar is not present in urine normally), few clinical problems
What enzyme will act on Galactose once it enters the cell?
Galactokinase (adds a Phosphate group to make Galactose 1-P)
Galactose 1-P interacts with UDP Glucose and is charged to UDP Galactose by what enzyme in a circular cycle?
Galactose 1-phosphate uridylyltransferase
What does Galactose 1-phosphate Uridylyltransferase do ?
It will charge Galactose 1-P to UDP Galactose while converting UDP glucose to Glucose 1-Phosphate for use in Glucose pathway and can be metabolized or maintain blood glucose levels
What does Epimerase do in the Galactose pathway?
It will convert UDP Galactose to UDP Glucose by modifying the carbon structure
-circular cycle to replenish and provide UDP Glucose to be transformed into Glucose 1-P
What is Nonclassical Galactosemia?
Galactokinase is not present
- can not be phosphorylated so it cant be trapped in cell
- few clinical problems
What is Classical Galactosemia?
Missing - Galactose 1-P Uridylyltransferase enzyme
- major clinical problem- Galactose 1-P will accumulate in cell as it is trapped but can not be broken down
What happens when Fructose 1-P builds up in liver in Hereditary Fructose Intolerance?
Decrease in free phosphate
Decrease in ATP availability (increase in AMP)
-will greatly effect gluconeogenesis and Glycogenolysis so blood glucose can be poorly regulated (hypoglycemia)
Lack of ATP levels caused by build up of Fructose 1-P in Hereditary Fructose Intolerance will inhibit what pathway?
Gluconeogenesis (energy requiring- synthesized from precursors)
Lack of free phosphate caused by build up of Fructose 1-P in Hereditary Fructose Intolerance will inhibit what pathway ?
Glycogenolysis (need phosphate to activate)
-negatively impacts blood glucose regulation (hypoglycemia)
What is the genotype of the parents of a child with Hereditary Fructose Intolerance when the parents do not present with it?
the child must have rr (autosomal recessive disease)
Parents must be Rr (heterozygous)
In PPP Glucose-6P is put through an oxidative pathway to make?
Ribulose 5-phosphate
What can Ribulose 5-phosphate do ?
- undergo non-oxidative pathway to convert back to intermediates for use in glycolysis
- be converted to Ribose -5-P for use in Nucleotide synthesis
What is the critical byproduct of converting Glucose-6P to Ribulose 5-P in the oxidative pathway?
NADP+ is converted to NADPH (essential to other reactions)
What is NADPH essential to?
Fatty acid synthesis
Glutathione reduction
Other reactions such as detoxification
In the Oxidative pathway portion of PPP, Glucose 6-P is ________ to Pentose Phosphates- 5 carbon sugar (Ribulose 5-P)
Decarboxylated - primary role of 5-C sugars is for Nucleotides
In the non-oxidative portion of PPP, the Pentose Phosphates can be converted back into what 2 examples of intermediates for use in glycolysis depending on needs of cell (pathway reverses)?
Fructose 6-P
Glyceraldehyde 3-P
Ratio of NADPH to NADP+ in cell is ______ than NADH to NAD+ in cell
Greater - more NADPH will be floating around than NADH because the NADH is oxidized rapidly in the ETC (more availability of NADPH in cell)
All tissues require _____ for reductive detoxification.
NADPH
NADPH is generated by ?
PPP and Malic enzyme pathway
PPP is critical in Red blood cells because it is only pathway that can create ______ that is necessary for ______ glutathione.
NADPH
reducing (necessary to bind Oxygen in reduced state)
In oxidative phase of PPP, Glucose 6-P is catabolized to Ribulose 5-P, and the oxidation of 1 mole of glucose generates ____ NADPH
2
What enzyme will be the first in PPP pathway acting on Glucose 6-P? (making NADPH)
Glucose 6-Phosphate Dehydrogenase (critical enzyme)
What is the intermediate created when Glucose 6-P is acted on by the Glucose 6-P dehydrogenase ?
6-Phosphogluconolactone
In the oxidative phase of PPP, there is an oxidation of the _____ and reduction of _______ in the first step.
Aldehyde (H-C=O) is oxidized into C=O
The intermediate 6-phosphogluconolactone undergoes rapid _______ in the Oxidative portion of PPP.
hydrolysis
What is 6-Phosphogluconolactae converted to after rapid hydrolysis in PPP oxidative pathway?
6-Phosphogluconate
What happens to 6-Phosphogluconate in PPP oxidative pathway (intermediate)?
Accepted by 6-Phosphogluconate dehydrogenase
- undergoes a decarboxylation reaction
- NADP+ is reduced to NADPH
- CO2 is released
What is the end product after 6-phosphogluconate is acted on by the dehydrogenase and is decarboxylated and reduced NADP+ to make NADPH (the second one in series)?
Ribulose-5 Phosphate (irreversible pathway product)
What part of PPP pathway is reversible and irreversible?
oxidative part is irreversible
non-oxidative is reversible
What enzymes does the non-oxidative phase of PPP involve?
4 types
Epimerase
Isomerase
Transketolase
Transaldolase
All reversible and direction depends on cell needs
What enzyme converts Ribulose 5-P to Ribose 5-P?
Isomerase
What enzyme converts Ribulose 5-P to Xylulose 5-P?
Epimerase
(changes the H structure on Carbon 3)
-reversible
What does the Transketolase enzyme do in the non-oxidative pathway of PPP?
Transfer of 2-C group from 5 carbon sugar to a different 5 Carbon sugar to make:
Glyceraldehyde 3-P
What is a coenyzme required for Transketolase reactions?
Thiamine Pyrophosphate (TPP)
What is an example of a Transketolase reaction?
Ribose 5-P to Glyceraldehyde 3-P
Describe the mechanism of the Transketolase enzyme in non-oxidative TPP pathway?
Cleaves the Carbon Carbon bond next to aldeyhyde and bonds to TPP where it can be transfered (2 Carbon moiety)
Where is the 2 Carbon moiety that is bound to TPP due to Transketolase transferred to ?
onto Ribose 5-P to then Generate 7 -Carbon sugar and release 3-Carbon sugar Glyceraldehyde 3-P
Transaldolase reactions involve the transfer of 3 Carbon chain from one sugar to another between ?
2 hydroxyl carbons adjacent to keto group
What is an example of a Transaldolase reaction?
Cleaving 3-C moiety from a 7 Carbon molecule and adding it to Glyceraldehyde 3-P to make Fructose 6-P for use in glycolysis to make pyruvate
For every 1 glucose 6-P molecule that enters the PPP oxidative pathway, how many NADPH, how man CO2 are made
2 NADPH
1 CO2
What are the two enzymes that can act on Ribulose 5-Phosphate that will determine its path in PPP
Epimerase
Isomerase
What will Epimerase do to Ribulose 5-P?
convert it to:
Xylulose 5-P that can make Glyceraldehyde 3-P that can either be used directly in Glycolysis or shunted into making Fructose 6-P
What will Isomerase do to Ribulose 5-P
convert it to Ribose 5-P
What are the paths that Ribose 5-P can take?
- Nucleotide synthesis
2. Acted on my Transketolase then Transaldolase
What does Ribose 5-phosphate get converted to when Transketolase first acts on it?
Sedoheptulose 7-P
What does Xylulose 5-P get converted to when Transketolase first acts on it ?
GLyceraldehyde 3-P
Ribose 5-P or ______ can interact with Xylulose 5-P using Transketolase enzyme to make Glyceraldehyde 3-P
Erythrose 4-Phosphate
What is the second step of the non-oxidative pathway involved for its enzyme? product?
Glyceraldehyde 3-P and Sedoheptulose 7-P interact using Transaldolase enzyme to add the 3 Carbon to Frutctose to make Fructose 6-P for using in GLycolysis
What is the secondary interaction that Erythrose 4-Phosphate can interact with if it does not interact with Transalodolase?
Transketolase acts on it and Xylulose 5-P
- Erythrose 4-P is converted to Fructose 6-P
- Xylulose is converted to Glyceraldehyde 3-P to use directly in glycolysis
Where is PPP regulated?
Oxidative phase
What is the regulatory enzyme (one that is regulated/inhibited) in PPP?
Glucose 6-dehydrogenase
-inhibited by high levels of NADPH (its own byproduct)
True or false:
NADPH is typically high in the cell to inhibit enzyme Glucose 6-P dehydrogenase from converting Glucose 6-P to 6-phosphogluconolactone
True
If the oxidative pathway in PPP is inhibited , can the non-oxidative pathway work?
Yes- allows cell to divert substrate in different pathways depending on needs
-can convert intermediates still
When a cell needs Ribose 5-P only what is likely to occur?
Only non-oxidative reactions
If the cells needs NADPH only, what will the pathways do?
Oxidative reactions make the NADPH
-Non-oxidative reactions will convert ribulose 5P to glucose 6-P to produce more NADPH
If the cells needs NADPH and Ribose 5-P , what will the pathways do
Oxidative pathways produce NADPH and ribulose 5-P
-the isomerase converts ribulose 5-P to ribose 5-P
If the cell needs Ribose 5-P only, what does the High levels of NADPH do ?
inhibts glucose 6-P dehydrogenase from making more NADPH
- Transketolase and Transaldolase are free to convert fructose 6-P and glyceraldehyde 3-P to ribose 5-P
What if the cell needs NADPH and Pyruvate, what do the PPP pathways do?
Both oxidative and non-oxidative reactions are used.
- Oxidative will make NADPH and Ribulose 5-P
- non-oxidative will convert ribulose 5-P to fructose 6-P and glyceraldehyde 3-P
- Glycolysis will convert the above intermediates to pyruvate
What detoxification pathways require NADPH?
- Reduction of oxidized glutathione
2. Cytochrome P450 monooxygenases
What reductive synthesis pathways need NADPH?
Fatty acid synthesis Fatty acid chain elongation Cholesterol synthesis Neurotransmitter synthesis Deoxynucleotide synthesis Superoxide synthesis
What type of transporter does RBC use to uptake GLucose?
Glut 1 transporter
What is the Cori Cycle?
active between muscle and liver and the RBC and liver
Glucose from the liver is taken up by the RBC and then the RBC creates 2 Lactate from 1 glucose which is taken up by liver and converted back to glucose in Gluconeogenesis
What are the two options that Glucose can go once inside the RBC?
- Phosphorylated to Glucose 6-P
2. Can either be converted to lactate in glycolysis or oxidized by the Pentose phosphate pathway to make NADPH
NADPH is required for ______ of glutathione in RBC.
reduction
Glutathione is a _______ compound that facilitates detoxification of free oxygen species that can damage cells/proteins. (Glutathione protects RBC)
tripeptide
What are the three AA that Glutathione is comprised of from top to bottom ?
Glycine
Cysteine (Sulfur R chain)
Glutamate
What is the free radical that is used as an example that Glutathione will detoxify?
Hydrogen peroxide
H2O2
____ molecules of Glutathione react with the enzyme ______ ______ to convert Hydrogen Peroxide to water (reduce it).
Two
Glutathione peroxidase
Who is reduced and who is oxidized in the reaction of Glutathione with Hydrogen peroxide in RBC?
H2O2 is reduced to water
Glutathione is oxidized to Glutathione disulfide (2 molecules linked by sulfide bond)
How does the product of Glutathione disulfide created when you detoxify free radicals (hydrogen peroxide) get recycled back to be used again?
- NADPH will donate its H to reduce GSSG back to two molecules of Glutathione
What enzyme does the NADPH use to reduce GSSG back to 2 molecules of Glutathione in RBC?
Glutathione reductase
What happens in RBC when there is a deficiency of Glucose 6-P dehydrogenase enzyme?
PPP pathway can not function to make NADPH (needed for glutathione recycling back from GSSG)
What is an effect in the RBC if NADPH is not being produced in PPP?
Free radicals and Hydrogen Peroxides can not be reduced and can damage cell
What happens to the RBC if free radicals and peroxides are allowed to roam free due to a deficency of the Glucose 6-P dehydrogenase that then causes NADPH to not be produced?
Hemolysis of RBC
Inability of Hemegloblin to bind oxygen (due to change to F3 state of iron)
What state does the Hb iron molecule need to be in to bind oxygen ?
Fe+2
What state does the iron in Hemeglobin change to if free radicals are not controlled
it is oxidized to a met-hemoglobin molecule and changed to a Fe+3 that can not bind oxygen
What is a Heinz body?
denatured hemoglobin in RBC (called met-Hb)that is caused by free radicals and peroxides
______ with only one copy of the defective allele for Glucose 6-P dehydrogenase can present with problems in RBC related to food and certain drugs with poor NADPH production.
Females
What type of disorder is Glucose-6-P dehydrogenase deficiency ?
X linked
Females can present with clinical symptoms if exposed to radical inducing compounds
Jaundice comes from the degregation of _______ from the RBC with excessive accumluation
Heme
In step one of RBC degradation, the Heme and Globin are separated and what happens to each?
- Globin is the AA and is degraded back to AA pathway
2. Heme is converted to Bilirubin
The conversion of Heme to Bilirubin occurs usually in the blood within a _______
macrophage
Bilirubin is______ soluble, so it must be bound to _______ to circulate in the blood
Not
Albumin
If the Bilirubin (insoluble version) or the soluble version Bilirubin Diglucuronide accumulates in the blood, it can cause ________
jaundice
Under normal conditions , bilirubin-albumin will go to liver where it is combined with ________ to generate a more soluble compound that can be excreted in feces and urine.
UDP-Glucuronate
What is Bilirubin called when it has been conjugated with UDP-glucuronate to be more soluble?
Bilirubin diglucuronide
What type of regulator is NADPH for Glucose 6-P Dehydrogenase ?
Allosteric effector (negative- too much NADPH will inhibit the enzyme)
