Pentose Phosphate Pathway & Pyrimidine/Purine Metabolism

What organisms is the Pentose Phosphate paathway present in?

Virtuall all organism

What does the Pentose Phosphate Pathway generate?

NADPH and ribose-5-phosphate

What is NADPH used for?

• Fatty acid

• cholesterol

• neurotransmitter

• nucleotide biosynthesis

What is ribose-5-phosphate used for?

• nucleoside

• amino acid

• coenzyme biosynthesis

2 Phases of Pentose Phosphate Pathway

• Oxidative

• Nonoxidative

Oxidative Pathway Reactant

• Glucose 6-Phosphate

• 2 NADP

• H2O

Oxidative Pathway Products

• Ribulose 5-phosphate

• CO₂

• 2 NADPH

• 2 H+

Nonoxidative Pathway Reactants

Ribulose 5-phosphate

Non Oxidative Pathway Products

• 2 fructose 6-phosphate

• glyceraldehyde 3-phodphate

Main Role of Nonoxidative Phase

Interconverting 3-, 4-, 5- ,6- ,7-carbon sugars

Main Role of Oxidative Phase

NADPH

Transketolase Reaction Mechanism

5-phosphoribosyl-a-D-1-pyrophosphate (PRPP)

Role of PRPP

central precursor in pyrimidine, purine, histidine and tryptophan metabolism

Formation of 5-phosphoribosyl-a-D-1-pyrophosphate (PRPP)

Ribose-5-phosphate → PRPP

Pyrimidine Biosynthesis Pathways

• De novo synthesis

• Salvage

What are pyrimidines assembled from?

• Bicarbonate

• Aspartate

• Glutamate

What does PRPP provide in Pyrimidine biosynthesis?

sugar moiety

Order of Pyrimidine biosynthesis?

1. Pyrimidine Ring

2. Bond to the sugar

Synthesis of cytidine triphosphate

Synthesis of thymidine monophosphate

What is UMP used for?

Common precursor for the remaining pyrimidine nucleotides

De novo Synthesis

the cellular metabolic pathway that constructs pyrimidine nucleotides (UMP, CMP, UTP, CTP, dTTP) from simple precursors—glutamine, aspartate, and bicarbonate

UMP

How are purine rings formed?

• De novo synthesis

• Salvage pathways

What are purine rings assembled from?

• bicarbonate

• aspartate

• glutamine

• glycine

• N10 -tetrahydrofolate

What does PRPP provide during purine biosynthesis?

PRPP provides the sugar moiety

Where is the purine base synthesized?

Purine base synthesized on the sugar

Synthesis of AMP and GMP

What enzyme forms 2’-deoxyribonucleotides?

Ribonuclease Reducatse

Mechanism for the formation of 2’-deoxyribonucleotide

Radical mechanism

Ribonculeotide Diphosphates

Substrates of 2’-deoxyribonucleotide

Role of NADPH in synthesis of 2’-deoxyribonucleotides

NADPH donates electrons indirectly to regenerate the reduced enzyme

Salvage of Purines and Pyrimidines

recycle bases and nucleosides from DNA/RNA degradation to synthesize nucleotides

Possible role of xanthine

Production of Uric Acid