Coordinate regulation of glycolysis and gluconeogenesis

13.11

Bypass 2

Freeze-clamp data

p. 549

Pasteur Effect: anaerobic cells exposed to air use less glucose

13.7

Substrate cycles in glycolysis and gluconeogenesis

Regulation can only be imposed on reactions displaced far from equilibrium

13.18

Control at bypass 2

13.19b

13.18

= F2,6 BP

13.19a

13.18

p. 553

(bifunctional)

Where does fructose-2,6-bisphosphate come from?

13.20,21

Regulation of bifunctional PFK-2/FBPase-2 by phosphorylation

P-enzyme: kinase !"bisphosphatase #

Un-P-enzyme: kinase #"bisphosphatase !

Kinase Phosphatase N C

S32

Coordinate regulation of glycolysis and gluconeogenesis

13.18

Bypass 1

Coordinate regulation of glycolysis and gluconeogenesis

13.18

Bypass 3

(not in liver, which expresses hexokinase IV)

Coordinate regulation of glycolysis and gluconeogenesis

13.18

Glycogen Metabolism

• Storage polymer• Osmotic advantage

Anaerobic glycolysis yields 2 ATP/glucose converted to lactate

Glucose from glycogen is already phosphorylated (glucose-1-P), so anaerobic glycolysis yields 3 ATP/glucose

• Rapid delivery of phosphorylated glucose:

total body glycogen has energy content = 6800 kJ

(total body glucose has energy content = 340 kJ)

2 major storage sites: ���•liver (2-10% wt)���•skeletal muscle (1-2%)

Glycogen granules in hepatocyte

13.26

p. 562

Glycogen breakdown: Glycogen phosphorylase

9.18b

13.25

Glycogen breakdown:

debranching enzyme

13.27

Glycogen breakdown

Glucose-6-Pphosphoglucomutase

glycolysis glycogen

Glucose-1-P

phosphorylase

Glycogen synthesis:Glycogen synthase

13.29

13.28

(phosphoanhydride exchange)

Synthesis of UDP-glucose

13.30

Complete oxidation of glucose-6-P in muscle yields 37 ATP:overall efficiency = 97% (36/37)

Branching enzyme