PLP vitamin phosphate that in the presence of phosphate, and to help enzyme kinase from , etc. and (different forms of B6) comes in and plays a very important role in biochemical reactions, including protein metabolism (amino acids), the neurotransmitters (acid gamma-aminobutyric and. serotonin, etc), glycogen and ... vitamin B6 is essential for the production of niacin (vitamin B3) from the amino acid tryptophan, etc. metabolism of hemoglobin (a protein found in red blood cells) and... there.