Enzyme Nomanclature

CP and ATP Use During Exercise Myokinase reaction 2 ADP ATP + AMP

- H - C - H - C - C - C - C - C = O - C - C = O - C - C = O O = C = O methyl H - C - H OH - alcohol C - C - C H - aldehyde C - C = O C - keto C - C = O Carbon dioxide OH - carboxylic acid O = C = O C - C = O

Glycolysis

Glycolysis -conversion of glucose to pyruvate, ATP & NADH + H+ ADP ATP O O Glucose Glucose-6-P (C6H12O6) - 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: C P P C C O O Glucose-6-P Fructose-6-P G-6-P Isomerase Glucose-6-P Fructose-6-P Isomerization (rearrangement of bonds) -(ie Aldose Ketose) -frees the #1-C to be phosphorylated

(Phosphofructokinase (PFK)-1) Glycolysis (cont.) Step 3: ATP ADP P C C P C C P O O (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.) Step 4: H O H H C H C O P H C O P H C OH C O + C O (aldolase) H H C OH H H C OH DHAP G-3-P H C O P DHAP= dihydroxyacetone phosphate (3-C) G-3-P= Glyceraldehyde 3 phosphate (3-C) H F-1,6 BP (6-C)

Glycolysis (cont.) Step 5: C O P C O P H C OH C O Triose - P Isomerase 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 H O O NAD+ NADH + H+ C C C OH C OH Pi C O P C O P G-3-P 1, 3, D.P.G -Phosphoglyceraldehyde dehydrogenase -NAD+ reduced -Aldehyde C oxidized to carboxylic acid

(Phosphoglycerate kinase) Glycolysis (cont.) Step 7: O O P O O- ADP ATP C C (2x) C OH (Phosphoglycerate kinase) C OH C O P C O P 1, 3, DPG 3 Phosphoglycerate *1, 3 DPG has a G of -11.8 (ATP = -7.3) Substrate level phosphorylation

(Phosphoglycerate mutase) Glycolysis (cont.) Step 8: O O- O O- C C C OH (Phosphoglycerate mutase) C O P C O P C OH 3 Phosphoglycerate 2 Phosphoglycerate *mutase - transfers a phosphate group

Phosphoenol pyruvate (PEP) Glycolysis (cont.) Step 9: O- O O O- C +H20 C (Enolase) C O P C O P C OH C 2 Phosphoglycerate Phosphoenol pyruvate (PEP) This is a dehydration step. WHY? G of PEP = - 14.8

Generate 2 ATP via substrate level phosphorylation Glycolysis (cont.) Step 10: O O- O O- C +H20 C ADP ATP C O P C O (Pyruvate kinase) C CH3 Pyruvate PEP Generate 2 ATP via substrate level phosphorylation

(Lactate Dehydrogenase) Glycolysis (cont.) step 6 Step 11: O O- O O- C C NADH + H NAD C O H C O H (Lactate Dehydrogenase) CH3 CH3 Lactate Pyruvate NADH + H oxidized to NAD pyruvate reduced to lactate

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 NET + 2 ATP via substrate-level phosphorylation Key regulated enzymes: PFK and HK

Glycolysis - Summary (cont.) Key enzyme: PFK (step 3) -allosterically regulated 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 transporter MCT 1-8 mMCT pmMCT

Localization of Krebs Cycle: Glycolysis occurs in the cytosol of cells. Pyruvate transported into the mitochondrion to be metabolized further. Mitochondrial Compartments: The matrix contains Pyruvate Dehydrogenase, enzymes of Krebs Cycle, and other pathways, e.g., fatty acid oxidation & amino acid metabolism.

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.

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

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

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

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%

PDH activation with Graded Exercise