2 Cofactors - Coenzymes and Ions


  • Can be Ions or Coenzymes

They are required as / to increase catalysis.

Ions as well as coenzymes can be loosely or tightly bound.
  • Coenzymes bound loosely = Cosubstrate
  • Coenzyme bound tightly = Prosthetic group


PLP (from Vit B6 – Pyridoxine )

  1. Transaminase
  2. Cystathione Beta synthase (deficient in HCU 1)
  3. Kinurinase


Confuser :
Most people confuse Melatonin and Melanin here.
Remember THB is required for melaTonin.
3 Hydroxylases
1. Tyrosine H – produces DOPA
2. Tryptophan H – helps in production of Serotonin which later forms  Melatonin
3.Phenylalanine H – produces Tyrosine

Thus THB is required for synthesis of :
  • Catecholamines
  • Melatonine
  • Serotonin

Note :

Tyrosine  produces -
  1. Catecholamines (uses THB in 1st step for this)
  2. Thyroid hormones
  3. Melanin ( here Tyrosinase enzyme is used which requires Cu++ as cofactor)

Vit B12

Homocystein Methyl transferase = Methionine Synthetase ( deficient in HCU 2 )

Selenium (Se)

Glutathione peroxidase

Iron (Fe)

Cytochrome oxidase  , Peroxidase , catalase

Manganese (Mn)

Superoxide Dismutase

Molybdenum (Mo)

Off topic MCQ point :
Most X-ray tubes use tungsten anode
But Mammography  uses molybdenum anodes. 

Xanthine Oxidase
Sulphide Oxidase

Magnesium (Mg)

Kinases (Hexokinase , Pyruvate kinase)
Glucose 6 phosphatase

Copper (Cu)

Cytochrome Oxidase

TPP (from Vit B1)

Alpha ketoglutarate dehydrogenase

Zinc (Zn)

Alcohol dehydrogenase
Carbonic anhydrase

Another frequent MCQ - Biotin is used in Carboxylation reactions.

MedicoNotebook - Founder : DrShiviMudgal , Co-Founder : DrAyushGoel


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