PENTOSE PHOSPHATE Pathway

• Glucose-6-PO4 Ribose-5-PO4

• Synthesize NADPH for fatty acid synthesis• Metabolize pentoses

Take Home: The PENTOSE PHOSPHATE pathway is basically used for the synthesis of NADPH and D-ribose. It plays only a minor role (compared to GLYCOLYSIS) in degradation for ATP energy.

CHOC-OH

HO-C

C-OHC-OH

CH2OP

COO-

C-OHHO-C

C-OHC-OH

CH2OP

CC-OH

HO-C

CC-OH

CH2OPO

O

NADP+

NADPH + H+

+ H2O

STAGE I (Oxidation)

Glucose-6-PO46-Phosphoglucono-- lactone

6-Phospho- gluconate

G-6-P dehydrogenase

Lactonase

COO-

C-OHHO-C-H

C-OHC-OH

CH2OP

C=OCH2OH

C-OHC-OH

CH2OP

CHO

C-OHC-OH

CH2OP

C-OHCO2

NADP+

NADPH + H+

Ru5P isomerase

Ru5P epimerase

Ribose-5-PO4

STAGE IIXylulose-5-PO4

Ribulose-5-PO4 (Ru5P)

6-Phosphogluconate

6-phosphogluconatedehydrogenase

CH2OH

C-OHC

CH2OP

C=OHO-

CH2OH

C-OHC

CH2OP

C=OHO-

CHO

C-OHC-OH

CH2OP

C-OH

C-OHC-OH

CH2OP

C-OHHO-C

C=OCH2OH

+

C-OHCH2OP

CHOTransketolase

Sedoheptulose-7-PO4Ribose-5-PO4

Xyulose-5-PO4

Glyceraldehyde-3-PO4

STAGE III

C-OHCH2OP

CHO

C-OHC-OH

CH2OP

C-OHHO-C

C=OCH2OH

C-OHC-OH

CH2OP

CHO

C-OHC-OH

CH2OP

HO-CC=OCH2OH

+

Glyceraldehyde-3-PO4

Fructose-6-PO4

Erythrose-4-PO4

Transaldolase

Sedoheptulose-7-PO4

C-OHC-OH

CH2OP

CHO CH2OH

C-OHC

CH2OP

C=OHO-+ C-OH

CH2OP

CHO

C-OHC-OH

CH2OP

HO-CC=OCH2OH

+

Transketolase

Erythrose-4-PO4Xylulose-5-PO4

Glyceraldehyde-3-PO4

Fructose-6-PO4

SUMMARY

5 + 5 3 + 7

7 + 3 4 + 6

4 + 5 3 + 6

Xylulose-5-PO4

Ribose-5-PO4

Glyceraldehyde-3-PO4

Fructose-6-PO4

Erythrose-4-PO4

Sedoheptulose-7-PO4

TK

TA

TK

3 Glucose-6-PO4 + 6 NADP+ + 3H2O

6 NADPH + 6H+ + 3CO2 + 2 Fructose-6-PO4

+ Glyceraldehyde-3-PO4

18 carbons

3 carbons 12 carbons

3 carbons

18 = 3 + 12 + 3

Note that:

2. Sedohepulose-7-PO4, erythrose-4-PO4 are strictly intermediates

3. Fructose-6-PO4 is never used as an intermediate4. Glyceraldehyde-3-PO4 is both an intermediate and final

product

1. For each glucose oxidized, 2 NADPHs are formed

The Dangers of Primaquine

Hemolytic anemia

GlutathioneNADPH

Reduced hemoglobin and cell lysis

G-6-P dehydrogenase

Glutathione reductase See p 423 in Textbook

Problem