Course Code: MBIO 202 Course Title: Microbial Metabolism -1 BSc in Microbiology.

1. P R I M E A S I A U N I V E R S I T Y
a mission with a vision
Assignment : 1,2.
Submitted to
Name: Aneeka Nawar fatema
Designation: Lecturer
Department: Microbiology
Institute: Primeasia University
Submitted by
Name: Md Azizul Haque
Student ID: 193016031
Course Code: MBIO 202
Course Title: Microbial Metabolism - I
Department: Microbiology
Date of Submission: January 13, 2021

2. Assignment : 01
Growth with aromatic hydrocarbon
Aromatic compounds produced by plants include mostly ligin and aromatic amino acids and
vitamins are consitituents of very organisms.
Characteristics of Aromatic Compounds
1) Cyclic structure.
2) Coplanar structure.
3) Each atom of the ring must have a p orbital to form a delocalized it system i.e. no atoms in
the ring can be spa hybridized instead all atoms must be sp2
hybridized (N.B. carbocation
and carbanions are sp2
hybridized or an unshared pair electrons).
4) Fulfill Huckel rule i.e. the system must have 4n + 2 pi electrons :
thus by calculating n value it will be an integral number i.e. n=0, 1, 2, 3,
Aromatic Compounds metabolizing microbes:-
Aromatic compounds are chemical compounds that consist of conjugated planar ring systems
accompanied by delocalized pi-electron clouds in place of individual alternating double and
single bonds. They are also called aromatics or arenes. The best examples
are toluene and benzene.
Acinetobacter
Alcaligenes
Agrobacterium
Bacilus
Aspergillus
Candida

3. Atypical aromatic compounds
Aromaticity also occurs in compounds that are not carbocyclic or heterocyclic; inorganic six-
membered-ring compounds analogous to benzene have been synthesized. For
example, borazine is a six-membered ring composed of alternating boron and nitrogen atoms,
each with one hydrogen attached. It has a delocalized π system and undergoes electrophilic
substitution reactions appropriate to aromatic rings rather than reactions expected of non-
aromatic molecules.
Quite recently, the aromaticity of planar Si6−
5 rings occurring in the Zintl phase Li12Si7 was experimentally evinced by Li solid-state NMR.
Metal aromaticity is believed to exist in certain clusters of aluminium, for example.
Homoaromaticity is the state of systems where conjugation is interrupted by a single
sp3
hybridized carbon atom.
Y-aromaticity is used to describe a Y-shaped, planar (flat) molecule with resonance bonds. The
concept was developed to explain the extraordinary stability and high basicity of
the guanidinium cation. Guanidinium is not a ring molecule, and is cross-conjugated rather than
a π system of consecutively attached atoms, but is reported to have its six π-electrons delocalized
over the whole molecule. The concept is controversial and some authors emphasize different
effects. This has also been suggested as the reason that the trimethylenemethane dication is more
stable than the butadienyl dication.
σ-aromaticity refers to stabilization arising from the delocalization of sigma bonds. It is often
invoked in cluster chemistry and is closely related to Wade's Rule.
Reactions
Aromatic ring systems participate in many organic reactions.
Aromatic substitution
In aromatic substitution one substituent on the arene ring, usually hydrogen, is replaced by
another substituent. The two main types are electrophilic aromatic substitution when the active
reagent is an electrophile and nucleophilic aromatic substitution when the reagent is a
nucleophile. In radical-nucleophilic aromatic substitution the active reagent is a radical. An
example of electrophilic aromatic substitution is the nitration of salicylic acid.

4. Coupling reactions
In coupling reactions a metal catalyses a coupling between two formal radical fragments.
Common coupling reactions with arenes result in the formation of new carbon–carbon bonds
e.g., alkylarenes, vinyl arenes, biraryls, new carbon–nitrogen bonds (anilines) or new carbon–
oxygen bonds (aryloxy compounds). An example is the direct arylation of perfluorobenzenes.
Hydrogenation
Hydrogenation of arenes create saturated rings. The compound 1-naphthol is completely reduced
to a mixture of decalin-ol isomers.
The compound resorcinol, hydrogenated with Raney nickel in presence of aqueous sodium
hydroxide forms an enolate which is alkylated with methyl iodide to 2-methyl-1,3-
cyclohexandione:
Cycloadditions.
Cycloaddition reaction are not common. Unusual thermal Diels–Alder reactivity of arenes can be
found in the Wagner-Jauregg reaction.Other photochemical cycloaddition reactions with alkenes
occur through excimers.

5. Dearomatization
In dearomatization reactions the aromaticity of the reactant is permanently lost.
Polycyclic aromatic hydrocarbons
Hexabenzocoronene is a large polycyclic aromatic hydrocarbon.
Polycyclic aromatic hydrocarbon
Polycyclic aromatic hydrocarbons(PAHs) are aromatic hydrocarbons that consist of
fused aromatic rings and do not contain heteroatoms or carry substituents. Naphthalene is the
simplest example of a PAH. PAHs occur in oil, coal, and tar deposits, and are produced as
byproducts of fuel burning (whether fossil fuel or biomass). As pollutants, they are of concern
because some compounds have been identified as carcinogenic, mutagenic, and teratogenic.
PAHs are also found in cooked foods. Studies have shown.

6. Refference:-
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7. Assignment : 02
Degradation of phenylalanine and tyrosine by homogentisate
pathway.
Figure 1: Tyrosine metabolism pathway

8. Phenylalanine
Phenylalanine is an essential α-amino acid with the formula C
9H
11NO
2. It can be viewed as a benzyl group substituted for the methyl group of alanine, or
a phenyl group in place of a terminal hydrogen of alanine. This essential amino acid is classified
as neutral, and nonpolar because of the inert and hydrophobic nature of the benzyl side chain.
The L-isomer is used to biochemically form proteins, coded for by DNA. Phenylalanine is a
precursor for tyrosine, the monoamine
neurotransmitters dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline), and
the skin pigment melanin. It is encoded by the codons UUU and UUC.
Phenylalanine is found naturally in the breast milk of mammals. It is used in the manufacture of
food and drink products and sold as a nutritional supplement for its
reputed analgesic and antidepressant effects. It is a direct precursor to
the neuromodulator phenethylamine, a commonly used dietary supplement. As an essential
amino acid, phenylalanine is not synthesized de novo in humans and other animals, who must
ingest phenylalanine or phenylalanine-containing proteins.
Figure:- Phenylalanine in humans may ultimately be metabolized into a range of different substances.

9. D-, L- and DL-phenylalanine
The stereoisomer D-phenylalanine (DPA) can be produced by conventional organic synthesis,
either as a single enantiomer or as a component of the racemic mixture. It does not participate
in protein biosynthesis although it is found in proteins in small amounts - particularly aged
proteins and food proteins that have been processed. The biological functions of D-amino acids
remain unclear, although D-phenylalanine has pharmacological activity at niacin receptor 2.[14]
DL-Phenylalanine (DLPA) is marketed as a nutritional supplement for its
purported analgesic and antidepressant activities. DL-Phenylalanine is a mixture of D-
phenylalanine and L-phenylalanine. The reputed analgesic activity of DL-phenylalanine may be
explained by the possible blockage by D-phenylalanine of enkephalin degradation by
the enzyme carboxypeptidase A.[15][16]
The mechanism of DL-phenylalanine's supposed
antidepressant activity may be accounted for by the precursor role of L-phenylalanine in the
synthesis of the neurotransmitters norepinephrine and dopamine. Elevated brain levels of
norepinephrine and dopamine are thought to have an antidepressant effect. D-Phenylalanine is
absorbed from the small intestine and transported to the liver via the portal circulation. A small
amount of D-phenylalanine appears to be converted to L-phenylalanine. D-Phenylalanine is
distributed to the various tissues of the body via the systemic circulation. It appears to cross
the blood–brain barrier less efficiently than L-phenylalanine, and so a small amount of an
ingested dose of D-phenylalanine is excreted in the urine without penetrating the central nervous
system.[17]
L-Phenylalanine is an antagonist at α2δ Ca2+
calcium channels with a Ki of 980 nM.[18]
In the brain, L-phenylalanine is a competitive antagonist at the glycine binding site of NMDA
receptor[19]
and at the glutamate binding site of AMPA receptor.[20]
At the glycine binding site
of NMDA receptor L-phenylalanine has an apparent equilibrium dissociation constant (KB) of
573 μM estimated by Schild regression[21]
which is considerably lower than brain L-
phenylalanine concentration observed in untreated human phenylketonuria.[22]
L-Phenylalanine
also inhibits neurotransmitter release
at glutamatergic synapses in hippocampus and cortex with IC50 of 980 μM, a brain concentration
seen in classical phenylketonuria, whereas D-phenylalanine has a significantly smaller effect.

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