Vitamin B3- metabolism

Vitamin B3- metabolism


VITAMIN B3 (NIACIN)

  • Vitamin B3 is also called as Nicotinic acid or nicotinamide.
  • Niacin can be synthesized tryptophan (1mg of the niacin formed from 60mg of tryptophan)

Active form of niacin-

  1. NAD+ (Nicotinamide Adenine Dinucleotide)
  2. NADP+ (Nicotinamide Adenine Dinucleotide Phosphate)

Coenzymes involved in reactions-

  1. Oxidoreduction reaction-

i) NAD+ linked dehydrogenases-

  • Isocitrate dehydrogenase
  • Malate dehydrogenase
  • α-ketoglutarate dehydrogenase
  • glutamate dehydrogenase
  • glyceraldehydes-3- P dehydrogenase
  • lactate dehydrogenase
  • β-hydroxyl acyl CoA dehydrogenase

ii) NADP+ linked dehydrogenases-

  • Glucose-6-P dehydrogenase in HMP shunt pathway

 2. ADP ribosylation

Metabolism & Excretions-

  • Nicotinamide excreted in urine are N1 –methyl nicotinamide and N1 –methyl 2-pyridone 5-carboxamide (2-pyridine).
  • N-methyl nicotinamide metabolized to methylpyridone-2- and 4-carboxamide
  • Nicotinic acid conjugated with glycine to form nicotinuric acid
  • Nicotinic acid methylated to trignonelline.
  • Daily recommended dose – 20mg/day 

Exam Important

  1. Vitamin B3 is also called as Nicotinic acid or nicotinamide.
  2. Niacin can be synthesized tryptophan (1mg of the niacin formed from 60mg of tryptophan)

Coenzymes involved in reactions-

  1. Oxidoreduction reaction-

i) NAD+ linked dehydrogenases-

  • Isocitrate dehydrogenase
  • Malate dehydrogenase
  • α-ketoglutarate dehydrogenase
  • glutamate dehydrogenase
  • glyceraldehydes-3- P dehydrogenase
  • lactate dehydrogenase
  • β-hydroxyl acyl CoA dehydrogenase

ii) NADP+ linked dehydrogenases-

  • Glucose-6-P dehydrogenase in HMP shunt pathway
  • Nicotinamide excreted in urine are N1 –methyl nicotinamide and N1 –methyl 2-pyridone 5-carboxamide (2-pyridine).
  • N-methyl nicotinamide metabolized to methylpyridone-2- and 4-carboxamide
  • Nicotinic acid conjugated with glycine to form nicotinuric acid
  • Nicotinic acid methylated to trignonelline.
  • Daily recommended dose – 20mg/day
Don’t Forget to Solve all the previous Year Question asked on Vitamin B3- metabolism

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