Enzyme Nomanclature

H - C - H

-H

C - C - C

- OH

C - C = O

-H

C - C = O-C

C - C = O

-OH

O = C = O

methyl

alcohol

aldehyde

keto

carboxylic acid

Carbon dioxide

Glycolysis

Glycolysis-conversion of glucose to pyruvate,

ATP & NADH + H+

O

C P

Glucose-6-P

O

C

(C6H12O6)

Glucose

ATP ADP

- IRREVERSIBLE (kinase reaction)--Glucokinase in liver, Hexokinase in skeletal muscle

- takes 1 ATP

- now locked in cell because phosphorylated compounds can’t cross cell membranes by diffusion and are not recognized by GLUT transporters

- Keeps intracellular free glucose levels very low to maintain facilitated diffusion gradient

Glycolysis (cont.)

Step 2:

O

C POC CP

Glucose-6-P Fructose-6-PG-6-P Isomerase

Isomerization (rearrangement of bonds)

-(ie Aldose Ketose)

-frees the #1-C to be phosphorylated

Step 3:

OC CP

(Phosphofructokinase (PFK)-1)

Fructose-6-P Fructose-1,6-Bisphosphate

Irreversible (kinase reaction)

- takes 1 ATP (-2 so far)

- phosphorylates fructose at 1-C

Glycolysis (cont.)

OC CP PATP ADP

Glycolysis (cont.)

Step 4:

H

CCC

CCC

H

H

HHH

H

O

HOO

P

O POHOH

H

C

C

H OOC

HO H

H

PCC

H

HH

OOH

P

COH

+

DHAP G-3-P

DHAP= dihydroxyacetone phosphate (3-C)

G-3-P= Glyceraldehyde 3 phosphate (3-C)

(aldolase)

F-1,6 BP (6-C)

Glycolysis (cont.)Step 5:

CCC OH

OO

P

Triose - P Isomerase

C O P

H OHC

COH

DHAP G-3-P

Isomerization - rearrangement of Bonds

- Ketose Aldehyde

- 1 G-6-P 2 G-3-P

Glycolysis (cont.)Step 6:

No Energy has been gained YET! -2 ATP

C

C O

OH

COH

P

1, 3, D.P.G

C

C O

OH

CO O

P

P

G-3-P

NAD+ NADH + H+

Pi

-Phosphoglyceraldehyde dehydrogenase

-NAD+ reduced

-Aldehyde C oxidized to carboxylic acid

Glycolysis (cont.)Step 7:

1, 3, DPG

C

C O

OH

C

P

OO P

(2x) C

C O

OH

C

P

O-O

3 Phosphoglycerate

ADP ATP

(Phosphoglycerate kinase)

*1, 3 DPG has a G of -11.8 (ATP = -7.3)

Substrate level phosphorylation

Glycolysis (cont.)

Step 8:

C

C O

OH

C

P

O-O

3 Phosphoglycerate

C

C OHO

C

P

O-O

(Phosphoglycerate mutase)

2 Phosphoglycerate

*mutase - transfers a phosphate group

Glycolysis (cont.)

Step 9:

C

C OH

O

C

P

O-O

2 Phosphoglycerate

(Enolase) C

C

O

C

P

O-O+H20

Phosphoenol pyruvate (PEP)

This is a dehydration step. WHY?

G of PEP = - 14.8

Glycolysis (cont.)

Step 10:

C

C

O

C

P

O-O+H20

PEP

ADP ATP

(Pyruvate kinase)C O

CO-O

CH3

Pyruvate

Generate 2 ATP via substrate level phosphorylation

Glycolysis (cont.)

Step 11:

C

CH3

O

CO-O

Pyruvate

NADH + H NAD

(Lactate Dehydrogenase)

C O

CO-O

CH3

Lactate

NADH + H oxidized to NAD

pyruvate reduced to lactate

H H

step 6

LDH Isozymes

LDH-H has a high Km for pyruvate (lactate to pyruvate)

LDH-M has a low Km for pyruvate (pyruvate to lactate)

Glycolysis - Summary

Step 1: - 1 ATP

Step 3: - 1 ATP

Step 6: + 2 NADH + H +

Step 7: + 2 ATP phoshoglyceraldehyde kinase

Step 10: + 2 ATP pyruvate kinase

+ 2 ATP via substrate-level phosphorylationNET

Key regulated enzymes: PFK and HK

Key enzyme: PFK (step 3)

-allosterically regulated

Glycolysis - Summary (cont.)

Activated by:

- AMP, ADP, PI

Inactivated by:

- ATP

- Citrate

- H+

CP and ATP Use During Exercise

Myokinase reaction 2 ADP ATP + AMP

Glycolytic Flux with Graded Exercise

Over rest: 7.5x 39.5x 65x 323x

Over 35% VO2 max ---- 5.2x 8.6x 43x

Cell to Cell Lactate Shuttle

Immunolabeling of LDH using antibodies conjugated with 15nm

gold particles

Monocarboxylic transporterMCT 1-8

mMCTpmMCT

The matrix contains Pyruvate Dehydrogenase, enzymes of Krebs Cycle, and other pathways, e.g., fatty acid oxidation & amino acid metabolism.

matrix

inner membrane

outer membrane

inter- membrane

space

mitochondrion

cristae

Localization of Krebs Cycle: Glycolysis occurs in the cytosol of cells.

Pyruvate transported into the

mitochondrion to be metabolized further.

Mitochondrial Compartments:

Inner membrane infoldings, called cristae, contain constituents of the respiratory chain & ATP Synthase.

The inner membrane is the major permeability barrier.

It contains various transport catalysts, including a carrier protein that allows pyruvate to enter the matrix.

Mitochondrial compartments

matrix

inner membrane

outer membrane

inter- membrane

space

mitochondrion

cristae

Pyruvate Dehydrogenase, catalyzes oxidative decarboxylation of pyruvate, to form acetyl-CoA.

H 3 C C C O

O O

C S

O

H 3 C Co A

HSCo A

N A D + N A D H

+ C O 2

P y r u v a t e D e h y d r o g e n a s e

p y r u v a t e a c e t y l - C o A

Pyruvate Dehydrogenase is a large complex, with multiple copies of each of 3 enzymes:E1, E2 & E3.

Acetyl CoA, a product of the Pyruvate Dehydrogenase reaction, is a central compound in metabolism.

a c e t y l - c o e n z y m e A

H 3 C C

O

S C o A

View an animation of the Pyruvate Dehydrogenase reaction sequence.

Activation of PDH with Graded Exercise

Regulation of PDH during exercise

*

% of CHO from:

Glycogen 74% 91% 93% 99%

Blood glucose 26% 9% 7% 1%

% of pyruvate into:

CAC 100% 34% 26% 7%

HLA 0% 66% 74% 93%