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CHAPTER 23
The Organic Chemistry of the Coenzymes, Compounds Derived from Vitamins
Important Terms
biotin
the coenzyme required by enzymes that catalyze carboxylation of a carbon
adjacent to an ester or a keto group.
coenzyme
a cofactor that is an organic molecule.
coenzyme A
a thiol used by biological organisms to form thioesters.
coenzyme
B
12
the coenzyme required by enzymes that catalyze certain rearrangement reactions.
cofactor
an organic molecule or a metal ion that an enzyme needs to catalyze a reaction.
competitive inhibitor
a compound that inhibits an enzyme by competing with the substrate for binding at
the active site.
dehydrogenase
an enzyme that carries out an oxidation reaction by removing hydrogen from the
substrate.
electron sink
a site to which electrons can be delocalized.
flavin adenine
a coenzyme required in certain oxidation reactions. It is reduced to
FADH
2
,
which
dinucleotide (FAD)
is a coenzyme required in certain reduction reactions.
heterocyclic compound
a cyclic compound in which one or more of the ring atoms is an atom other than
carbon.
lipoate
a coenzyme required in certain oxidation reactions.
mechanism-based inhibitor
an inhibitor that inactivates an enzyme by undergoing part of the normal catalytic
(suicide inhibitor)
mechanism.
molecular recognition
the recognition of one molecule by another as a result of specific interactions.
nicotinamide adenine
a coenzyme required in certain oxidation reactions. It is reduced to NADH, which
dinucleotide
1
NAD
2
is a coenzyme required in certain reduction reactions.
nicotinamide adenine
a coenzyme that is reduced to NADPH, which is a coenzyme required in certain
dinucleotide phosphate
reduction reactions.
1
NADP
2
nucleotide
a heterocycle attached in the
b
-position to the anomeric carbon of a phosphorylated
ribose.