Clinical Presentation Curriculum

A Guide toIntermediary Metabolism

Jack Blazyk, Ph.D.2003-2004

Design of M et abolism

A ct ivat ed Pr ecur sor s M acr omolecules

Pr ecur sor s

GlycogenT r iglycer ides

Pr ot eins

U D P- GlucoseF at t y A cyl- CoA

A minoacyl t - RN A

GlucoseF at t y A c idsA mino A cids

CH E M I CA LPO W E R

O 2

E N E RGY

CO 2

H 2 ON H 3

H E A T

60%

40%

O x idat ion(Combust ion)

A nabolism(B iosynt hesis)

Cat abolism

2

In an actively functioning pathway,

the G for ALL reactions is NEGATIVE

Allosteric Regulation

Covalent Modification(e.g., reversible phosphorylation)

OR

Genetic Regulation

Thermodynamics

Enzyme Regulation

3

High-Energy Phosphates

Enol

Example

Phosphoenolpyruvate (PEP)

Acyl

Example

1,3-Bisphosphoglycerate

Amino

Example

Creatine phosphate

Pyro (Phosphoanhydride)

Example

Adenosine triphosphate (ATP)

Hydrolysis of Phosphates

Enol

-15

Acyl

-10

Amino

-10

Pyro

-7

Adenosine Pool

ATP

ADP

AMP

Hydrolysis of ATP

4

NAD+ + 2e- + H+ NADHOxidized Reduced

Nicotinamide Adenine Dinucleotide

Electron Transfer

NADP+ + 2e- + H+ NADPHOxidized Reduced

Nicotinamide Adenine Dinucleotide Phosphate

FAD + 2e- + 2H+ FADH2

Oxidized Reduced

Flavin Adenine Dinucleotide

Coenzyme A

ADP + Pantothenic Acid + SH

CoA - SH

CoA - S ~ C – CH3

O

Acetyl-CoA

Acyl Group Transfer

5

4. C4 C4 + 4e-

Citric Acid Cycleor

Tricarboxylic acid (TCA) Cycle

orKrebs Cycle

Located in mitochondrial matrix

Citrate

- COO-

Citric Acid

1. C2 + C4 C6

3. C5 C4 + CO2 + ~P + 2e-

2. C6 C5 + CO2 + 2e-

Oxidative Decarboxylations

Sneak Preview

6

Citrate Synthase Aconitase

Isocitrate Dehydrogenase

-KG Dehydrogenase

Oxidative Decarboxylations

Succinate ThiokinaseSuccinate

Dehydrogenase

FumaraseMalate

Dehydrogenase

CH3 - C - S - CoA

3 H2O

3 NAD+

1 FAD

GDP + Pi

O

In CoA - SH

2 CO2

3 NADH + 3 H+

1 FADH2

GTP + H2O

Out

7

Tap-Off Points

Malate

NADP+

PEP Carboxykinase

Malic Enzyme

Anaplerotic Pathway

Pyruvate Carboxylase

Pyruvate Oxaloacetate

ATP + CO2 ADP + Pi

Allosterically activated by Acetyl-CoA

Biotin (a water-soluble B vitamin) is a coenzyme

NADPH + H+ + CO2

Pyruvate

8

Oxidative Phosphorylation

Electron Transport Chain = Respiratory Chain

4 Membrane-Bound Complexes

• I – NADH-Q Reductase

• II – Succinate-Q Reductase

• III – Cytochrome Reductase

• IV – Cytochrome Oxidase

2 Mobile Electron Carriers

• Ubiquinone (Coenzyme Q)

• Cytochrome c

Complex INADH-Q Reductase

Transfers electrons from NADH to Q

NADH + H+ + Q NAD+ + QH2

• Flavin Mononucleotide (FMN)

• Iron-sulfur (Fe-S) proteins

Complex IISuccinate-Q Reductase

Transfers electrons from Succinate to Q

Succinate + Q Fumarate + QH2

• Flavin Adenine Dinucleotide (FAD)

• Iron-sulfur (Fe-S) proteins

Complex IIICytochrome Reductase

Transfers electrons from QH2 to Cyt c

QH2 + 2Cyt c(Fe+3) Q + 2H+ + 2Cyt c(Fe+2)

• Cytochrome b (2 types)

• Iron-sulfur (Fe-S) proteins

• Cytochrome c1

Complex IVCytochrome Oxidase

Transfers electrons from Cyt c to O2

2Cyt c(Fe+2) + ½O2 + 2H+ 2Cyt c(Fe+3) + H2O

• Cytochrome a

• Cytochrome a3

• Copper (Cu)

9

Chemiosmotic Mechanism

• Proposed by Peter Mitchell

• Proton Motive Force

• PMF = pH +

10

ATP Production via CAC and Ox Phos

3 NADH ~9 ATP

1 FADH2 ~2 ATP

1 GTP 1 ATP

~12 ATP per Acetyl-CoA

GTP + ADP GDP + ATP

Regulation of CAC and Ox Phos

• Availability of Acetyl-CoA

• Availability of O2

• Energy Charge =

• Respiratory Control

[ATP] + ½ [ADP]

[ATP] + [ADP] + [AMP]

X

X

Electron Transport

Inhibitors

CO

CN -

N3-

Rotenone

11

Oxidative Phosphorylation

Inhibitors

Oligomycin

Atractyloside

X

X

Uncouplers

2,4-

Dinitrophenol

+ H+

NO2NO2

O -

NO2NO2

OH

H+

H+

H+

X

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39R-COOH

40Fatty Acid Oxidation

41

42

43Fatty Acid Biosynthesis

44Regulatio

n

45

46Triglyceride Metabolism

47Lipogenesis

Lipolysis

48

49Amino Acid Metabolism

50

Amino Group Shuttles

Matrix Cytoplasm

Liver

Urea Cycle

From Harper’s Biochemistry, Murray et al., 25th ed., 2000, Fig. 31-14

51

Well-Fed Conditions

Gly

coly

sis

Glycogenesis

PentoseShunt

Fatty AcidSynthesis

CholesterolSynthesis

TriglycerideSynthesis

52

Gly

coly

sis

PentoseShunt

Fatty AcidSynthesis

CholesterolSynthesis

TriglycerideSynthesis

Well-Fed Conditions

53

Well-Fed Conditions

Glycogenesis

54

Insulin

RBC

Liver

Muscle

Adipose

Brain

Gut

Portal Vein

Lymphatics

Glucose

Glycogen

Glucose

CO2 + H2O

Protein

TG

Urea

Pancreas

Glucose

TGPyruvate

Lactate

Lactate

Chylomicrons

VLDL

Glycogen

CO2 + H2O

CO2 + H2O

Well-Fed State

55

Glu

con

eog

enes

is

Fatty AcidOxidation

Ketone Body Synthesis

GlycogenolysisFasting Conditions

56

Fatty AcidOxidation

TriglycerideBreakdown

No Uptake

Fasting Conditions

57

No Uptake

Fatty AcidOxidation

Ketone BodyUtilization

Fasting Conditions

58

Early Fasting State

Glucagon

RBC

Liver

Muscle

Adipose

Brain

Gut

Portal Vein

Lymphatics

Glycogen

GlucoseG

luco

se

CO2 + H2O

Pancreas

Pyruvate

CO2 + H2OCO2 + H2O

FA

FA

Lactate

Lactate

59

Extended Fasting State

Glucagon

RBC

Liver

Muscle

Adipose

Brain

Gut

Portal Vein

Lymphatics

CO2 + H2O

Pancreas

Pyruvate CO2 + H2O

KB

Lactate

FA

Glycerol

FA

CO2 + H2O

Protein

Cortisol

Glucose

Urea

60