This document summarizes two enzyme-catalyzed reactions: (1) the interconversion of ethanol and acetaldehyde catalyzed by alcohol dehydrogenase, and (2) the interconversion of esters and carboxylic acids catalyzed by acetylcholinesterase. It provides details on the enzymes, cofactors, reaction mechanisms, and substrates involved in each reaction. The document was authored by Al Mamun for their M.Sc session from 2016-2017.

1. WELCOME
ENZYME-CATALYZED INTERCONVERSION
OF
I. ETHANOL and ACETALDEHYDE
II. ESTER and CARBOXYLIC ACID
AL MAMUN
13024508
M.Sc
Session:2016-2017

2. ENZYME-CATALYZED INTERCONVERSION
OF
Ethanol and Acetaldehyde

3. CONVERSION

4. Alcohol dehydrogenase(ADH)
Alcohol dehydrogenases (ADH) are a group of
dehydrogenase enzymes that occur in many organisms
and facilitate the interconversion between alcohols and
aldehydes or ketones with the reduction of nicotinamide
adenine dinucleotide (NAD+ to NADH).
In humans and many other animals, they serve to break
down alcohols that otherwise are toxic
In yeast, plants, and many bacteria, some alcohol
dehydrogenases catalyze the opposite reaction as part
of fermentation to ensure a constant supply of NAD+

5. The alcohol dehydrogenases comprise a group of several
isozymes that catalyse the oxidation of primary and
secondary alcohols to aldehydes and ketones,
respectively, and also can catalyse the reverse reaction.
Alcohol dehydrogenases (ADH)

6. PROPERTIES OF ADH
ADH is a dimeric protein.
ADH is activated by glutathione and EDTA and
inhibited by heavy metals.
Optimum is pH 8.6 though pH closer to 7 considered
optimum for acetaldehyde reduction. ADH becomes
increasingly unstable with higher pH values.
The specific configuration of the active site makes it
stereospecific and ADH will only remove the pro-R
hydrogen from the alcohol group.
All animal ADH enzymes are active as dimers and
therefore two sub-units come together to form a
functioning enzyme

7. Active site of ADH
All forms of ADH have a common zinc domain per sub-
unit formed from specific amino acid residues
The zinc ion is co-ordinated to the sulphur atoms of two
cysteine residues and the nitrogen atom of a histidine
residue.
It serves to electrostatically stabilise the oxygen
molecule of the alcohol group of ethanol.

9. Nicotinamide adenine dinucleotide
(NAD+)
Nicotinamide adenine dinucleotide (NAD+) is a coenzyme
found in all living cells.
Nicotinamide adenine dinucleotide exists in two forms: an
oxidized and reduced form abbreviated as NAD+ and
NADH respectively.
In metabolism, nicotinamide adenine dinucleotide is
involved in redox reactions, carrying electrons from one
reaction to another.

10. The compound is a dinucleotide, because it consists of
two nucleotides joined through their phosphate groups.
One nucleotide contains an adenine base and the other
nicotinamide.

11. The NAD+ binding domain is also a crucial feature of the
enzyme as this is a cofactor required for reaction and is
linked to the ethanol binding site by an alpha helix.
NAD+

12. REACTION

13. MECHANISM
Only one of the protons of Et-OH is abstracted and is added
to a specific side of NAD+
So this was the whole process of conversion

14. ENZYME-CATALYZED INTERCONVERSION
OF
ester and carboxylic acid

15. CONVERSION
H2O

16. Acetylcholinesterase(AChE)
Acetylcholinesterase also known as AChE or
acetylhydrolase, is the primary cholinesterase in the body.
This is an enzyme present in the synapses between
neurons, catalyzes the hydrolysis of acetylcholine, a
neurotransmitter that triggers muscle contraction.
It is an enzyme that catalyzes the breakdown of
acetylcholine and of some other choline esters.

17. If the action of acetylcholinesterase is inhibited,
acetylcholine in the synapse does not get hydrolyzed and
thus continues to trigger muscle contractions, resulting
in paralysis and death in severe cases.

18. REACTION
AChE

19. MECHANISM
Like many hydrolytic enzymes, the reaction proceeds via a
covalent enzyme-substrate intermediate, formed when
the acyl group of acetylcholine is initially transferred to an
active-site serine.
A water nucleophile then attacks this ester, driving off
acetate(carboxylic acid) and completing the hydrolysis.

20. This was the whole process of conversion

21. THANKS ALL OF
YOU