Lack of B6 results in defects in protein metabolism.
PLP found in enzymes that catalyze reactions involving amino acids, e.g. isomerizations, decarboxylations, R-group removal or replacements.
Most frequent reaction is a transamination, where the a-amino group of a.a. is transferred to carbonyl group of a-keto acid --> new a.a. made or is excreted.
PLP binds covalently with Lys residue in active site --> keeps PLP from running away.
Biotin
Synthesized by intestinal bacteria.
Prosthetic coenzyme is called biocytin - covalently linked to Lys residue in active site.
Involved in carboxyl group transfer reactions and ATP-dependent carboxylations.
E.g. pyruvate carboxylase
pyruvate + HCO3- ---> oxaloacetate
Binds to HCO3- and acts as a CO2 carrier.
Folic Acid or Folate
Found in green leafy vegetables, liver, yeast.
Coenzyme form is tetrahydrofolate.
Used by enzymes that transfer 1-C units as methyl groups (CH3-).
Another folate coenzyme is tetrahydrobiopterin - used in hydroxylases.
Pantothenic Acid
Used in coenzyme A formation.
Reactive center is -SH group
Key in all acyl-group transfers
Coenzyme form is phosphopantethine - added to serine residue of protein --> acyl carrier protein (ACP) --> important in fatty acid synthesis.
Vitamin B12 or cobalamin
Found in organ meat (kidney and liver).
It is a prosthetic coenzyme.
Ring structure similar to heme, with cobalt atom in center.
Involved in molecular rearrangements.
Deficiency in B12 results in pernicious anemia (decreased production of blood cells from bone marrow).
Vitamin C or ascorbic acid
Found in fresh fruit and vegetables.
Participates in hydroxylation reactions, e.g. collagen synthesis.