Cofactors and Chemistry

Biotin

Chemical structure of biotin	3D representation
Biotin is a cofactor that is involved with carboxylation reactions. (an organic acid is added to a compound using CO2 in the form of bicarbonate). In a carboxylation reaction ATP must be hydrolyzed to activate the CO2 as shown below. Then a carboxybiotin intermediate is formed that is the carboxylating agent. The CO2 is added in an Aldol Reaction most frequently requiring a metal ion to drive the formation of the transition state.
Formation of bicarbonate (HCO3-) from CO2 occurs in water and does not require enzyme catalysis
CO2 + H20 HCO3- + H+
SOME ENZYMES USING THIS COFACTOR
pyruvate carboxylase An important Enzyme of gluconeogenesis. We will learn more about this in Module 6
acetylCoA carboxylase An important enzyme in fatty acid synthesis.