Vitamin Pyridoxine 
And Biotin

INTRODUCTION OF VITAMIN

  • Organic molecules, essential for the normal growth and development, required in tiny amounts
  • Cannot be synthesized by mammalian cells, must be supplied in the diet

THE CLASSIFICATION OF VITAMINS

  • Water-soluble

Thiamine VB1

Riboflavin VB2

Niacin 

Pantothenic acid

Pyridoxine VB6

Biotin VB7

Folic Acid VB11 ? VB9 

CobalaminVB12

Vitamin C VC 

  • Fat-solubleVA, VD, VE and VK 

WATER SOLUBLE VITAMINS: CHARACTERISTICS

  • Essential 
  • Organic Structure
  • Non-energy Producing
  • Micronutrients
  • Stability 
  • Bioavailability
  • Toxicity

THE B VITAMINS

Chief Functions – Important as Coenzymes

i) Thiamin

ii) Riboflavin

iii) Niacin

iv) Pantothenic Acid & 

v) Biotin 

         Involved in Energy Metabolism

Vitamin B-6 involved in Protein 

         Metabolism

– Folate & Vitamin B-12 involved

         in Cell Replication

– Therapeutic doses of Niacin 

         lower cholesterol 

WATER SOLUBLE VITAMINS VS.
FAT SOLUBLE VITAMINS

WATER SOLUBLE VITAMINS VS.
FAT SOLUBLE VITAMINS

Coenzymes

Coenzymes OF VITAMINS

Vitamins are derived from a variety of foods.  

PYRIDOXINE (VITAMIN B6)

  • Vitamin B6 is used to collectively represent

   the three compounds namely:

i. Pyridoxine

ii. Pyridoxal and 

iii. Pyridoxamine

  • Active form of Pyridoxine:

Pyridoxal phosphate (PLP)

DIETARY SOURCES

Rich sources are dried yeast, rice polishing, wheat germs, cereals, legumes, oil seeds, egg, milk, meat, fish and green leafy vegetables.

RDA

  • Requirement of vitamin Bis related to dietary protein intake, as it is involved as coenzyme in many metabolic reactions of amino acid metabolism
  • Adults : 2 mg/day
  • Infants : 0.3 – 0.4 mg/day
  • Vitamin B6 compounds are pyridine derivatives
  • They differ from each other in the structure of a functional group attached to 4th carbon in the pyridine ring

i. Pyridoxine: Primary Alcohol

ii. Pyridoxal: Aldehyde form while

iii. Pyridoxamine: Amine

PYRIDOXINE
4,5-Bis(hydroxymethyl)-2-methylpyridin-3-ol

PYRIDOXINE
4,5-Bis(hydroxymethyl)-2-methylpyridin-3-ol

CO – ENZYME FORM

Pyridoxal phosphate

Pyridoxal phosphate

BIOCHEMICAL FUNCTIONS

  • Transamination
  • Decarboxylation
  • Sulphur containing amino acid
  • Heme Synthesis
  • Production of Niacin

DEFICIENCY MANIFESTATION

  • Neurological manifestation
  • Dermatological manifestation
  • Hematological manifestation

BIOTIN

SYNONYMS:

  • Bios
  • Vitamin H
  • Vitamin 7
  • Co-enzyme R
  • Anti egg white injury factor

Biotin is a sulphur containing B-complex vitamin.

  • In old literature Biotin was known as anti egg white injury factor.
  • Biotin was isolated in 1942 by Vincent du Vigneaud, who was awarded Nobel prize in 1955.

DIETARY SOURCES

  • Normal bacterial flora of the gut will   provide adequate quantity of Biotin
  • Moreover, it is distributed ubiquitously in plant and animal tissues
  • Liver, yeast, peanut, soybean, milk and 

egg yolk are rich sources.

RDA

About 200 – 300 mg will meet the daily requirements.

CHEMISTRY

  • Biotin is a hetrocyclic monocarboxylic acid
  • Sulphur containing water soluble B vitamin
  • Structure of the compound was worked out by du Vigneaud
  • It consist of two fused rings, 

i. Imidazole and 

ii. Thiophene derivative

STRUCTURE BIOTIN

STRUCTURE OF BIOTIN

CO-ENZYME ACTIVITY OF BIOTIN

  • Biotin present in liver as Biocytin (active form of Biotin)
  • Biotin act as a co-enzyme for: 

Carboxylation Reactions

  • In the First Step:

A molecule of CO2 is captured by Biotin

  • The resulting carboxybiotin contains carboxyl group covalently attached to the nitrogen of Biotin molecule.
  • The energy required for this reaction is provided by ATP
  • In the second step: 

Activated carboxyl group is transferred to the substrate and A free biotynyl enzyme is regenerated.  

BIOCHEMICAL FUNCTIONS
Biotin Requiring CO2 Fixation Reactions

  1. Acetyl CoA carboxylase:
  • This enzyme adds CO2 to acetyl coA to  form malonyl CoA.
  • This is the rate limiting reaction in biosynthesis of fatty acids

2. Propionyl CoA Carboxylase:

  • It is another Biotin requiring Enzyme

3. Pyruvate Carboxylase:

  • Fixes CO2 to Pyruvate to form Oxaloacetate

4. Leucine:

  • Required for conversion of β methyl crotonyl CoA to β methyl gluconyl CoA

BIOTIN ANTAGONIST

  • Avidin, a protein present in egg white has great affinity to biotin
  • Hence intake of raw (unboiled) egg may cause biotin deficiency
  • Biotin deficiency was experimentally produced by giving raw egg white
  • Therefore biotin was originally named as anti-egg-white-injury-factor

BIOTIN DEFICIENCY

Biotin deficiency may be produced by:

  • Large quantity of avidin
  • Prolonged use of antibacterial drugs
  • Very rarely, holocarboxylase synthetase enzyme is deficient or absent
  • Leiner’s disease occurs in breast fed young infants with persistent diarrhea

DEFICIENCY SYMPTOMS

  • Dermatitis
  • Atrophic Glossitis
  • Hyperesthesia
  • Muscle pain
  • Anorexia
  • Hallucinations
BIOTIN DEFICIENCY
BIOTIN DEFICIENCY
LEINER’S DISEASE IN INFANTS
LEINER’S DISEASE IN INFANTs

Other Biochemistry Notes :-

Pyrimidine metabolism

Purine Metabolism

Cardiac Biomarkers

. Blood Metabolism (Heme synthesis and breakdown)

Haemoglobinopathies

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And Biotin”

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