Serine Metabolism

Property	Description
Chemical formula	C₃H₇NO₃
Type	Non-essential amino acid
Nature	Polar amino acid
Side chain	Hydroxymethyl group (-CH₂OH)
Major function	One-carbon metabolism

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Biosynthesis of Serine

Serine is synthesized from the glycolytic intermediate 3-phosphoglycerate.

Steps in Serine Synthesis

Step 1: Formation of 3-Phosphohydroxypyruvate

3-Phosphoglycerate      →        3-Phosphohydroxypyruvate

Enzyme

• • 3-Phosphoglycerate dehydrogenase

Step 2: Formation of 3-Phosphoserine

3-Phosphohydroxypyruvate   +  Glutamate     →    3-Phosphoserine

Enzyme

• • Phosphoserine aminotransferase

Step 3: Formation of Serine

3-Phosphoserine   →   Serine

Enzyme

• • Phosphoserine phosphatase

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Conversion of Serine to Glycine

Serine is the major precursor of glycine.

Reaction

Serine  +  THF   ⇌  Glycine  +  N5,N10-methylene THF

Enzyme

• Serine hydroxymethyl transferase

Cofactors

• Pyridoxal phosphate (Vitamin B₆)
• Tetrahydrofolate (THF)

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Metabolism

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Degradation of Serine

Serine is degraded mainly by deamination.

Reaction

Serine  →  Pyruvate  +  NH3​

Enzyme

• Serine dehydratase

Importance

• Pyruvate enters glucose metabolism
• Serine is glucogenic

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Specialized Products Synthesized from Serine

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Functions of Serine

1. Role in Glycine Formation

Serine is the major precursor of glycine.

Reaction

Serine  +  THF  ⇌  Glycine  +  N5,N10-methylene THF

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2. One-Carbon Metabolism

Serine provides one-carbon units required for:

• Purine synthesis
• Thymidylate synthesis
• DNA synthesis

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3. Phospholipid Synthesis

Serine participates in synthesis of:

• Phosphatidylserine
• Cell membrane phospholipids

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4. Sphingolipid Formation

Serine combines with palmitoyl-CoA to form sphingolipids.

Importance

• Brain development
• Myelin formation
• Nerve function

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5. Energy Production

Serine is converted into pyruvate and enters:

• Glycolysis
• TCA cycle

Reaction

Serine  →  Pyruvate  +  NH3​

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6. Protein and Enzyme Synthesis

Serine is present in:

• Structural proteins
• Enzymes
• Active sites of many proteins

Function	Importance
Protein synthesis	Structural component of proteins
Glycine synthesis	Precursor of glycine
One-carbon metabolism	Provides carbon units through THF
Purine and pyrimidine synthesis	DNA and RNA formation
Phospholipid synthesis	Cell membrane formation
Sphingolipid synthesis	Nervous system function
Energy metabolism	Converted to pyruvate
Cysteine synthesis	Sulfur amino acid metabolism

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Clinical Significance 

1. Serine Deficiency Disorders

Defect in serine biosynthesis causes:

• Microcephaly
• Seizures
• Developmental delay
• Mental retardation

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2. Cancer Metabolism

Rapidly growing tumor cells require serine for:

• DNA synthesis
• RNA synthesis
• Cell proliferation

Increased serine metabolism is seen in many cancers.

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3. Nervous System Function

Serine is required for:

• Sphingolipid synthesis
• Myelin formation
• Brain development

Deficiency may cause neurological abnormalities.

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4. One-Carbon Metabolism

Serine provides one-carbon units through THF.

Importance

Required for:

• Purine synthesis
• Thymidylate synthesis
• DNA formation

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5. Vitamin B₆ and Folate Deficiency

These vitamins are essential for serine-glycine interconversion.

Deficiency Causes

• Impaired amino acid metabolism
• Reduced nucleotide synthesis
• Neurological defects

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6. Energy Metabolism

Serine is converted into pyruvate and contributes to:

• Glucose metabolism
• ATP production

Reaction

Serine  →  Pyruvate  +  NH3​

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Disorders 

Disorder	Defect
3-Phosphoglycerate dehydrogenase deficiency	Defective serine synthesis
Phosphoserine phosphatase deficiency	Reduced serine formation
Serine deficiency syndrome	Neurological abnormalities