Group H Phosphofructokinase 2 Presentation

Phosphofructokinase 2 (PFK2) \

Fructose bisphosphatase 2 (FBPase2)

Fates

of

Pyruvate

Structure

Glucagon

Epinephrine

G6P

in liver and muscle

Glycogen synthase B

(inactive)

GSD Type IV: Andersen's

cAMP-dependent

Protein Kinases

(A & C)

a (1->4) glucose

oligosaccharide

• accumulation of long, insoluble glycogen chains
• hepatomegaly and cirrhosis
• infantile cirrhosis and FTC --> usually fatal

Insulin

Glycogen synthase A

Protein

Phosphatase 1

can only elongate already existing chains of glucose

makes 1->4 glycosidic linkages

anomeric carbons

-glucose transferred to non-reducing end of chain (the end where the anomeric carbon of the terinal sugar is linked by a glycosidic bond to another compound)

Hexose Monophosphate Shunt

Glucose

non-reducing end

n+1 residues

Glycogenin

amylo-a(1->4)->(1->6)-

transglucosidase

can serve as primer

WBC Phagocytosis

Lysosomal a(1->4)

glucosidase

GSD Type II: Pompe's Disease

"branching enzyme"

• Inborn lysosomal enzyme deficiency
• Generalized (primarily liver, heart, skeletal muscle)
• Glycogen accumulates in lysosomes
• Normal blood sugar levels
• Massive cardiomegaly
• Early death (<2 yrs) usually occurs from heart failure
• Normal glycogen structure
• "Pompe's trashes the pump [heart]"

Glycogen

Synthesis and Breakdown

Reductive biosynthesis

6P Gluconate

-MPO system uses NADPH oxidase to consume oxygen in the phagolysosome and create a "respiratory burst" which kills ingested microbes

Reduction of

hydrogen peroxide

Pi

G6P

Glucose

-and other reactive oxygen species formed from the partial reduction of molec O2

-reactive intermediates can damage DNA, proteins, and unsaturated lipids

-RBCs are totally dependent on PPP to generate NADPH to maintain glutathione in its reduced form

Glucose 6-Phosphatase

Synthesis of nitric oxide

Glycogen

UDP-Glucose

G6Pase not found in muscle cells

GSD Type I: von Gierke's

-requires Arg, O2, and NADPH as substrates for NO synthase

-NO is endogenous vasodilator; acts through guanylate cyclase

Glucose

NADPH

main stores in skeletal muscle and liver

6PG DHase

• Glycogen is rapidly-mobilizable
• Allows glucose release from the liver and kidney in the absence of dietary glucose
• Muscle glycogen is degraded in exercise to provide tissue with energy
• When glycogen stores depleted, specific tissues synthesize glucose from amino acids

• sever fasting hypoglycemia
• normal glycogen structure
• hepatorenomegaly

• hyperlipidemia
• fasting lactic acidosis
• nonresponsive to glucogneogenic stimuli

ATP synthesis during

muscle contraction

maintain blood glucose during early stages of a fast

Cytochrome P450

monooxygenase system

6PG Hydrolase

Lactose

synthesis in mammary glands

ATP

NADH

NADPH

-reduces steroid, drug, and other chemicals in the mitochondria and SER

Lactase

(B-galactosidase)

in intestinal mucosa cell membrane

H2O

Specific transporters

necessary

Endoplasmic reticulum

Galactose

Galactitol

Aldolase reducatase

GSD Type V: McArdle's Syndrome

• present in liver, kidney, retina, lens, nerve, seminal vesicles, and ovaries
• physiologically unimportant unless galactose is high
• elevated galactitol can cause cataracts

Cytosol

Ribulose 5P

2 Pi

PPi

Phosphorylase

Kinase B (inactive)

Galactokinase

Pyrophosphatase

GSD Type Ib: G6P Translocase Deficiency

Glycerol-P

Glycerol

• Only skeletal muscle affected
• Temporary weakness and cramping after exercise
• No rise in blood lactate during strenuous exercise
• Normal mental development
• Myoglobinemia and myoglobinuria
• Fair to good prognosis
• High level of muscle glycogen w/ normal structure

Galactokinase deficiency

• Causes galactosemia and galactosuria
• Causes galactitol accumulation if galactose present in diet

6P Gluconolactone

Debranching

Enzyme

Galactose 1P

ATP

• Affects liver, kidney, and intestine
• Severe fasting hypoglycemia
• Hepatomegaly (fatty liver)
• Progressive renal disease
• Growth retardation and delayed puberty
• Hyperlacticacidemia and hyperuricemia
• Normal glycogen structure; increased glycogen stored
• Treatment: Nocturnal gastric infusions of glucose or regular administration of uncooked cornstarch

Dihydroxyacetone

Phosphate

cAMP-dependent

Protein Kinase

Glucagon

Epinephrine

Protein Phosphatase 1

glycerol kinase

UDP-glucose

pyrophosphorylase

glycerol 3-P dehydrogenase

Glucose 6-Phosphate

Dehydrogenase

Glucose 6-Phosphate

Translocase

Insulin

in liver only

hydrolytic cleavage of

last residue [an a(1->6) bond] in a branch

Galactose 1P

uridyltransferase

UDP-hexose

4-epimerase

GSD Type VI: Hers' Disease

Phosphorylase

Kinase A (active)

in liver and adipose

G6PD Deficiency

Ribose 5P

UTP

Classic galactosemia

• Uridyltransferaes deficiency
• Autosomal recessive (1:23k births)
• Causes galactosemia and galactosuria, vomiting, diarrhea, and jaundice
• Accumulation of Gal-1-P in nerve, lens, liver, and kidney tissue causes liver damage, severe mental retardation, and cataracts
• Antenatal diagnosis is possible by chorionic villus sampling
• Treatment: Rapid diagnosis and removal of galactose (therefore, lactose) from diet

ATP

• defective hepatic glycogen phosphorylase
• defective glycogenolysis, but GNG is fine
• mild fasting hypoglycemia
• normal glycogen structure
• early childhood presentation of hepatomegaly may improve with age

Brings G6P across ER membrane

Only in liver and kidney

ATP

Glycogen

phosphorylase A

Inactive Glycogen

phosphorylase B

UDP-Galactose

storage in adipose tissue

export from liver as VLDL

Hexokinase, Glucokinase

-characterized by hemolytic anemia caused by the inability to detoxify oxidizing agents

-X-linked family of deficiencies caused by >400 different mutations in G6PD gene (mostly point mutns)

-increased resistance to malaria in female carriers

-most severe manifestation is in RBCs, where PPP is required to obtain NADPH --> Heinz bodies; rigid and nondeformable RBCs which are removed by macrophages in spleen and liver

-precipitating factors: oxidant drugs (SMX, antimalarials, chloramphenicol); favism; infection; neonatal jaundice

Insulin

Protein phosphatase 1

Transketolases

and

Transaldolases

cleavage of a(1->4) glycosidic bonds at non-reducing ends of glycogen chains

NADPH

Lactose

Glycoproteins

Glycolipids

Glycosaminoglycans

Phosphoglucomutase

Mg+2

-liver

-pancreatic B cells

-hi Km and Vmax

Glucose uptake by Na+ independent facilitated diffusion transport is mediated by a family of GLUT transporters.

• GLUT1 --> RBCs and brain
• GLUT3 --> neurons
• GLUT4 --> adipose tissue and skeletal muscle
• Insulin increases the expression of GLUT4
• GLUT2 --> liver, kidney, B-cells...glucose uptake OR release

-low Km (hi affinity)

-low Vmax

Glycogen (n-1)

and

Insulin

Glucose-1-phosphate

Glucose-6-Phosphate

glucose 1,6-bisphosphate intermediate

G6P

Triacylglycerol

acyltransferase

G6P, ATP, Glucose

in liver

G6P, ATP

in muscle

Ca+2, AMP

in muscle

Mechanism

thiamine-dependent

Glucagon,

F6P

promotes transcription of the GK gene

Glucose uptake (against its conc. gradient) in the epithelial cells of the intestine, renal tubes, and chorid plexus requires co-transportation of Na (with its gradient).

Insulin,

Glucose

Glucose + glycogen phosphorylase A is better substrate for protein phosphatase 1 --> glycogen degradation not required

Ca+2 - calmodulin complex binds to and activates physphorylase kinase without the need for phosphorylation. Maximal activation when phosphorylated and bound to Ca/Calmodulin.

Insulin inhibits muscle glycogen phosphorylase by increasing uptake of glucose --> increase in G6P levels --> allosteric inhibition of glycogen phosphorylase

causes GK to bind reg. prot. in nucleus

releases GK from reg. prot.

AMP binds directly to muscle glycogen phosphorylase, causing activation without phosphorylation.

Glucose + glycogen phosphorylase B can not be allosterically activated by AMP

Phosphoglucose

Isomerase

Xylulose 5P

R1 is typically saturated

R2 is typically unsaturated

R3 can be either

Glycogen

ATP

Fructose-6-Phosphate

Mannose

Mannose 6P

Hexokinase

Phosphomannose isomerase

Debranching Enzyme

transfers 3 residues of shortened branch

Insulin

Sedoheptulose 7P

GSD Type III: Cori's Disease

Glucose

Glucagon

Erythrose 4P

Phosphofructokinase-2

desaturation (addition of cis-DBs) in the ER

Fructose

Bisphosphatase-2

can be further elongated in the ER and mitoch

Glucagon is a binds to a TM receptor coupled to a trimeric G protein. Receptor changes conformation and favors the binding of GTP to the alpha subunit of the G protein. The activated G protein activates Adenylyl Cyclase which converts to cAMP. cAMP is an allosteric activator of Protein Kinase A, which in turn phosphorylates protein targets, such as the PFK2/FBPase2 complex.

A high insulin/glucagon ratio decreases cAMP levels.

In general:

-Insulin causes protein de-phosphorylation

-Glucagon causes protein phosphorylation

Pi

ATP

dephosphorylated form is active

phosphorylated form is active

ATP

AMP + PPi

CoA

• fasting hypoglycemia (milder than Type I)
• normal blood lactate levels
• glycogen has short outer branches
• glycogenolysis is defective; GNG is fine
• hepatomegaly in infancy

NADPH

Aldolase reductase

Mg+2

ATP

Found in: lens, retina, Schwann cells, liver, kidney, placenta, RBCs, ovaries, sperm, and seminal vesicles

ATP

Phosphofructokinase-1

Fructose 1,6-

bisphosphatase

Fatty acid

Fatty acyl CoA

AMP

F26BP is an essential activator of PFK-1

Hexokinase

F26BP inhibits F16BPase

Fructose-2,6-

Bisphosphate

In liver and kidney

low affinity for fructose

fatty acyl-CoA synthetase

ATP, Citrate

AMP

Sorbitol

H2O

palmitate

prevented by

hi F26BP

16C, saturated

Sorbitol dehydrogenase

NADPH

Found in: liver, ovaries, sperm, and seminal vesicles

Why?

• Sperm use fructose as major CHO energy
• Liver can convert any available sorbitol to glycolytic intermediate

Glyceraldehyde 3P

Sorbitol cannot pass efficiently through cell membranes, so when it is formed in hyperglycemic conditions (DM) with little or no sorbitol DHase (such as in the lens, retina, kidney, and nerve cells), it can cause swelling as a result of water retention. This can in turn result in catacact formation, peripheral neuropathy, and vascular problems associated with diabetes.

Hereditary fructose intolerance

• Absence of aldolase B --> intracellular trapping of F1P
• Hypoglycemia, vomitting, jaundice, hemorrhage, hepatomegaly, and hyperuricemia
• Can cause hepatic failure and death
• Therapy: Rapid detection and removal of fructose and sucrose from the diet

ATP

Fructose-1,6-Bisphosphate

ATP

Glyceraldehyde

Fructose

Sucrose

Fructose

1-Phosphate

Sucrase

Fructokinase

Aldolase A/B

Essential fructosuria

• Lack of fructokinase
• Autosomal recessive (1:130k births)
• Benign, asymptomatic condition
• Fructose accumulates in urine

in small intestine

Triokinase

liver, kidney, small intestine

entry to cell is insulin-independent

CO2

Aldolase B

liver, kidney,

small intestine

Phosphotriose

Isomerase

NADH

Dihydroxyacetone

Phosphate

de novo

Fatty Acid Biosynthesis

Glyceraldehyde-3-Phosphate

Malonyl CoA

Remember: 2x per glucose from here on down

Pi

Alcohol

Dehydrogenase

BPG Mutase

+2NADPH

NAD+

fatty acid

synthase

Glyceraldehyde-3-Phosphate

Dehydrogenase

esp in RBCs

-> increases

Hb release

of O2

Glycerol

CO2

NADH

Electron

Transport

Chain

ATP

each addition of mal-CoA requires

2NADPH, produces CO2, and

elongates the fatty acid chain by 2Cs

1,3-Bisphosphoglycerate

2,3-BPG

Glycerol

Kinase

Malonyl CoA

-via mal-asp shuttle

+2NADPH

In the presence of arsenic, G3P --> 3PG w/o forming NADH

fatty acid synthase shuttles the growing chain

back and forth between an acyl carrier protein

and the thiol group of a cysteine residue

Mg+2

Glycerol-P

Phosphoglycerate

Kinase

ATP

"substrate-level phosphorylation"

3-Phosphoglycerate

Triacylglycerides

Phosphoglycerides

Phosphoglycerate

Mutase

Anaerobiosis

ATP

CO2

Feed-forward regulation

2-Phosphoglycerate

Acetyl CoA

Malonyl CoA

acetyl CoA carboxylase

three carbons

two carbons

active polymer

Enolase

Oxaloacetate

requires biotin

CO2

GTP

H2O

GTP

Oxaloacetate

Phosphoenolpyruvate

cytosolic

PEP Carboxykinase

ATP-Citrate lyase

cytosolic

PEP Carboxykinase

CO2

Insulin, F16BP

Mg+2

Glucagon

Insulin

Pyruvate

Kinase

Increases PEPCK gene transcription

Decreases PEPCK gene transcription

Glucagon, ATP, Ala

citrate

cAMP-dependent PK

phosphorylation in presence of

glucagon and epinephrine

cAMP-dependent phosyl'n

--> PEP to gluconeogenesis

Glucagon

Insulin

ATP

long-chain

fatty acyl-CoA

PK deficiency (autosomal recessive) is second most common cause (after G6PDH def.) of enzyme-related hemolytic anemia

• restricted to RBCs
• severe chronic HA requires regular cell transfusions
• partially compensated for by increased production of 23BPG

Increases PEPCK gene transcription

Decreases PEPCK gene transcription

NADH

NAD+

protein phosphatase

dephosphorylation in

presence of insulin

NADH

ATP, CoA

cytosolic

Malate

Dehydrogenase

Pyruvate

Lactate

Lactate Dehydrogenase

high-calorie, high-CHO diets also

cause an increase in Ac-CoA carboxylase

synthesis over the long-term

Citrate

(negative regulator of PFK-1)

• Lactate formation favored by hi NADH/NAD+ ratio
• LDH direction also depends on [pyruvate] and [lactate]

Malate

acetyl CoA carboxylase

(inactive dimer)

Pyruvate transporter

NADH

consumes energy

Cytosol

Malate-Aspartate Shuttle

-uses malate to carry NADH across mitochondrial membrane for use in the ETC

Aspartate aminotransferase

Malate dehydrogenase

NADH

Glutamate

Aspartate

Malate

Oxaloacetate

a-ketoglutarate

Mal-aKG antiporter

Glu-Asp antiporter

Glutamate

Malate

Oxaloacetate

Aspartate

a-ketoglutarate

NADH

Malate dehydrogenase

Aspartate aminotransferase

Mitochondrion

NADH

3-Hydroxybutyrate

Acetone

NADH

Diabetic ketonuria

Acetoacetate

• in uncontrolled DM I (insulin-dep), high FA

degrad'n --> xs Ac-CoA and slows TCA

• xs Ac-CoA --> ketones -->

urinary excretion + fruity breath

• elevated blood ketones (more H+ in less volume) --> acidemia -->

dehydration and ketoacidosis

Pyruvate

Ketone Body Synthesis

Co-A

• occurs in liver mitoch
• acetoacetate and 3-hydroxybut transported to peripheral tissues where they are re-converted to Ac-CoA and oxidized by the TCA
• major source of energy for peripheral tissues, including the brain (esp important during prolonged fasting)

HMG CoA

NAD+

NADH, ATP,

and Ac-CoA

Pyruvate

Dehydrogenase

cAMP-independent protein kinase

-phosphorylates E1 in presence of Ac-CoA, ATP, NADH -PK inhibited by pyruvate (thereby activating E1)

NADH

Phosphoprotein phosphatase

-dephosphorylates E1 in presences of Ca+2

Component enzymes: multiple copies of each in tight physical association

-pyruvate dehydrogenase, E1, decarboxylase --> requires TPP

-dihydrolipoyl transacetylase, E2 --> requires lipoic acid and Co-A

-Dihydrolipoly dehydrogenase, E3 --> requires FAD and NAD+

HMG CoA Synthase

PDH Deficiency

-most common cause of congenital lactic acidosis

-pyruvate converted to lactate via LDH

-can cause damage to cerebral cortex, basal ganglia, and brainstem

-X-linked dominant (E1 gene)

CO2

to kidney via blood

Acetyl CoA

Propionyl CoA

TCA and FA synthesis

link to GNG:

Acetyl-CoA is positive regulator of pyruvate carboxylase

final step of odd-chain oxidation

only product that is gluconeogenic

Some urea diffuses from blood to intestine where bacterial urease cleaves it to CO2 and NH3.

-In patients with kidney failure, a greater amount of urea is transfered to the gut, and bacterial urease contributes significantly to hyperammonemia. Neomycin reduces the number of bacteria responsible for this NH3 production.

short/med chain

Fatty acids

CO2

short/med chain

Fatty acids

These carbons are not released during their first turn around the TCA

ATP

-2 per glucose

Pyruvate

Carboxylase

Ac-CoA

Urea

Occurs in liver and kidney

Uses biotin as a coenzyme

Purposes:

-provide substrate for gluconeogenesis

-replenish TCA cycle intermediates

Muscle pyruvate carboxylase forms OAA only to replenish TCA

OAA cannot cross mitoch. membrane --> converted to malate

CoA

Arginine

3-ketoacyl CoA

ACAT

Fumarate

Malate

To mitochondria and TCA via the malate shuttle

H2O

Ac-CoA for FA synthesis

Arginase

Citrate Synthase

CoA-SH

almost exclusively in the liver

Primary regulation by availability of substrate

Inhibitor of PFK-1

(glycolysis)

ATP, NADH, Succinyl Co-A,

FA derivatives

Insulin, Ca+2,

ADP

Activator of Ac-CoA carboxylase

(FA synthesis)

Citrate

Oxaloacetate

Arginosuccinate

lyase

Ornithine

Carnitine

long-chain

Fatty acyl CoA

Ornithine

NADH

Fatty acyl

CoA

Fatty acyl CoA

obtained from diet

synth from Lys and Met

dehydrogenase

Fatty

Acid

B-oxidation

Aconitase

NAD+

(2nd oxidation)

mitochondrial

Malate

Dehydrogenase

Fluoroacetate

Urea Cycle

transamination of Asp

Arginosuccinate

Malate

Carbamoyl-P

Isocitrate

occurs in the liver

Carnitine palmitoyl-

transferase I

Carnitine palmitoyl-

transferase II

Ornithine trans-

carbamoylase

aka CAT I

aka CAT II

CoA

NADH

N-acetyl-glutamate

absolutely required

Carbamoyl phosphate

synthetase I

RCO-Carnitine

Citrulline

acyl-CoA

dehydrogenases

Pi

rate-limiting step

3-hydroxyacyl CoA

Fumarase

2 ATP

Isocitrate

Dehydrogenase

(oxidation)

NADH

arginine

rate-limiting

CoA

Med-chain FA CoA DH deficiency (MCADD)

Arginosuccinate

synthetase

Tri-Carboxylic

Acid Cycle

• autosomal recessive disorder
• inability to oxidize FAs w/ <12 Cs
• symptoms of hypoglycemia
• Tx: avoid prolonged fasting;

CHO+, protein+, FA- diet

H2O

Ca+2, ADP

ATP, NADH

malonyl-CoA

AMP

FADH2

CO2

ATP

Ammonia transfer to liver

-Glutamine synthetase in most tissues produces Gln which is transported in blood to liver, where glutaminase cleaves Gln producing Glu and NH3.

-Transamination of pyruvate in muscle forms alanine which is transported in blood to liver. Pyruvate produced in the liver can be converted to glucose through GNG.

CO2

NH3

enoyl CoA hydratase

enoyl CoA

(hydration)

urea cycle

CO2

biotin

Vit B12

Aspartate

Fumarate

glutamate

alpha-Ketoglutarate

a-ketoglutarate

purine synthesis

NAD+ or

NADP+

Oxaloacetate

Ca+2

NAD+ primarily used in oxidative deamination

NADPH used in reductive amination

Phe and Tyr catabolism

H2O

CoA-SH

Glutamate dehydrogenase

ATP

ATP, GTP, NADH, succinyl-CoA

oxidative deamination

aKG Dehydrogenase

Complex

Phe

Tyr

Succinate

Dehydrogenase

Complex of three enzymes; very similar to PDH

-requires TPP, lipoic acid, FAD, NAD+, and CoA

FADH2

a-ketoglutarate

Glutamate

NADH

ADP

GDP

ATP

GTP

CO2

Glucose

Succinyl Co-A

Succinate

Succinyl CoA

Synthetase

AA catabolism

CoA-SH

GTP

Clinical correlation: aminotransferases in blood indicate damage to cells.

-Liver disease: elevated plasma AST and ALT

-Other: myocardial infarction and muscle disorders

-ALT forms pyruvate from Ala

-AST shuttles N from Glu to Asp

during AA catabolism (Asp to urea cycle)

a-amino acid

aminotransferases

all require pyridoxal phosphate

(deriv of vit B6)

transamination

a-keto acid

NH3