(Riboflavin) (168-R. S 7th)RIBOFLAVIN (B2) - Riboflavin through its coenzyme FMN and FAD takes part in a variety of cellular oxidation-reduction reaction* The flavin coenzymes (mostly FAD and lesser extent FMN) participate in many redox reactions responsible for energy production.* Enzymes that use flavin coenzymes (FMN or FAD) are called flavoproteins* Galactoflavin is an antimetabolite of riboflavin* **FMN and FAD acts as coenzyme in various H-transfer reactions in metabolism- The hydrogen is transported by reversible reduction of the coenzyme by two hydrogen atoms added to the 'N' at position 1 and 10, thus forming dihydro or leucoriboflavin (161- Rana Shinde 6th)NIACIN (Nicotinic acid, P. P. factor)* The coenzymes NAD* and NADP+ operate as hydrogen and electron transfer agents by virtue of reversible oxidation and reduction* **60 mg of tryptophan can give rise to 1 mg of Niacin* * High pellagra is more common in persons who staple diet is maizeTHIAMINE (B1) (anti beri-beri or antineuritic vitamin)* It has a specific coenzyme thiamine pyrophosphate (TPP) which is mostly associated with carbohydrate metabolismCYANOCOBALAMINE (B12) (Anti pernicious anemia factor, extrinsic factor of castle, Animal protein factor)* There are two coenzyme forms of B12 (a) 5-Deoxyadenosyl cobalamine, (b) Methylcobalamine* Biologically active forms are "cobamide coenzymes" act, as coenzyme with various enzymes.* *Cobamide coenzyme do not contain the "cyano-" group attached to cobalt but instead there is an Adeninine Nucleoside, which is linked to cobalt by a C-CO bond.Transcobalamine 1Transcobalamine II1. Source-probably Leucocytes increased in myelo proliferative states2. Plasma level = 60 mg/L1. Source is Liver2. Plasma level = 20 mg/L