Cofactors - Coenzymes and Ions

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Cofactors

• 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

Cofactor	Enzyme
PLP (from Vit B6 – Pyridoxine )	Transaminase Cystathione Beta synthase (deficient in HCU 1) Kinurinase
THB  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 - Catecholamines (uses THB in 1st step for this) Thyroid hormones 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 Arginase
Molybdenum (Mo) Off topic MCQ point : Most X-ray tubes use tungsten anode But Mammography  uses molybdenum anodes.	Xanthine Oxidase Sulphide Oxidase Dinitrogenase
Magnesium (Mg)	Kinases (Hexokinase , Pyruvate kinase) Glucose 6 phosphatase
Copper (Cu)	Tyrosinase Cytochrome Oxidase
TPP (from Vit B1)	Alpha ketoglutarate dehydrogenase
Zinc (Zn)	Alcohol dehydrogenase Carbonic anhydrase

Another frequent MCQ - Biotin is used in Carboxylation reactions.

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