1. Cofactor Binding
Cofactor bind with the inactive enzyme/Apo enzyme
to activate the enzyme OR the binding of cofactor
with Apo enzyme convert it to Holo enzyme
Some cofactors are inorganic, such as the metal atoms
zinc, iron, and copper in various oxidation states.
Others, such as most vitamins, are
organic. Cofactors are generally either bound tightly to
active sites, or may bind loosely with the enzyme
2. Cofactor
Cofactor
Non protein chemical copound
Required for enzyme activity as catalyst
Considered as helper molecules
Assist the biochemical transformation
Cofactors may be organic or inorganic
5. 1.Inorganic cofactors
These are also devided into two group
Metal ions
Iron –sulfur clusters
Metal ions
Metal ions are common cofactors
Some enzymes, referred to as metalloenzymes, cannot
function without a bound metal ion in the active site
6. ..
In nutrition, the list of essential trace elements reflects
their role as cofactors.
In humans these are
includes iron, magnesium, manganese, cobalt, copper,
zinc, and molybdenum.
Although chromium deficiency causes impaired
glucose tolerance, no human enzyme that uses this
metal as a cofactor has been identified
Iodine is also an essential trace element, but this
element is used as part of the structure of thyroid
hormones rather than as an enzyme cofactor
7. Example
Mg2+ is used in glycolysis.
In the first step of converting glucose to glucose 6-
phosphate
before ATP is used to give ADP and one phosphate
group,
ATP is bound to Mg2+ which stabilizes the other two
phosphate groups so it is easier to release only one
phosphate group.
9. Iron –sulfur clusters
Iron-sulfur clusters are complexes of iron and sulfur atoms
held within proteins by cysteinyl residues.
They play both structural and functional roles, including
electron transfer, redox sensing, and as structural modules.
These clusters have many unique properties that are not
found in amino acids or other organic compounds.
[Fe-S] clusters participate in electron transfer, substrate
binding/activation, iron/sulfur storage, regulation of gene
expression, and enzyme activity
Definition
An iron-sulfur cluster is a unit comprising two or
more iron atoms and bridging sulfur ligands.
11. 2.Organic cofactors
Organic cofactors also called as coenzyme
Coenzyme are non-protein ,low molecular weight
organic compound that participating in enzymatic
reaction
Can not function alone
Can be used several time when paired with enzyme
12. ,
They have two groups or sides
prosthetic group
cosubstrate
Prosthetic group is tightly covalently and permanently
bound to protein
Cosubstrate is transiently bound to protein may be
released from protein at some time and then rebind
Vitamin and essential nutrients are common example
of coenzyme
13. Function of coenzyme
The coenzyme is essential for the biological activity of
the enzyme.
• A coenzyme is a low molecular weight organic
substance, without which the enzyme cannot exhibit
any reaction.
• One molecule of the coenzyme is able to convert a large
number of substrate molecules with the help of
enzyme.
14. Nicotinamide Adenine Dincleotide
(NAD+ )
• This is a coenzyme synthesized from Nicotinamide, a
member of vitamin B complex.
• The structure of NAD+ could be written as:
Nicotinamide-Ribose-P-P-Ribose-Adenine
• The reversible reaction of lactate to pyruvate is
catalyzed by the enzyme lactate dehydrogenase, but
the actual transfer of hydrogen is taking place on the
coenzyme, NAD+ .
