Amino Acid

               Amino acid   

—  Organic compounds containing two

    functional  groups i.e. –NH2 group &

    -COOH group.

—   Monomer & Building blocks of protein

     molecules.

a)      4-OH Proline            :-  Plant cell wall protein

b)      5-OH Lysine             :-  Both a & b found in 

                                           collagen.

c)       6-N-CH₃ Lysine        :-  Myosin

d)      Desmosine               :-  Elastin

e)      γ-Carboxy glutamate :- Prothrombin

—  Most of the amino acid found in body are exist in

      α-amino acids.

—   There could be β,γ,δ & ω etc.

  Eg. GABA, β-Alanine ( component of pantothenic acid, co-A)

Abbreviation

—  In all common amino acid, 1^st 3 letter of their

   name is used as abbreviation except Asperagine

   [Asn], Glutamine[Gln], Tryptophan[Trp],

   Isoleucine[Ile].

—  Cysteine          - Cys

—  Histidine          - His

—  Valine              - Val

—  Serine              - Ser

—  Methionine       - Met

—     Alanine            - Ala

—     Glycine            - Gly

—     Arginine           - Arg           

—     Aspartate         - Asp

—    Glutamate         - Glu

—    Phenylalenine   - Phe

—    Tyrosine             -   Tyr

—    Leucine              -   Leu

—    Proline                -   Pro

—    Threonine           -   Thr

—    Lysine                 -   Lys

Symbol

—  In many amino acid, 1^st letter of their name is

   used as symbol & in others, symbol has been

   agreed by convention.

1. Unique 1^st letter :- In unique amino acid, 1^st

      letter of their name is used as symbol.

     Eg.

—  Cysteine       -   C

—  Histidine       -   H

—  Isoleucine       -   I

—  Valine             -   V

—  Serine             -  S

—  Methionine      -  M

2. When the one or more than one amino acid

      has been written[represented]by same initial

      alphabet, then the most commonly occurring

      amino acid have a priority to indicated by 1^st

       letter.

–   Alanine            - A

–   Glycine            - G

–   Leucine            - L

–   Proline             - P

–   Threonine        - T

3. Similar sounding name:- while pronouncing

      these amino acid, sounding of one alphabet

      is dominent & these are used as symbol.

—   Asparagine             N

—   Glutamine               Q

—   Arginine                   R

—   Aspartate                 D

—   Glutamate                E

—  Phenylalanine            F

—   Tyrosine                     Y

—   Tryptophan                W

4. In rest of the amino acid, one letter before

     the alphabet starting the name of amino acid

     is used as symbol.

Eg. Lysine    - K

Classification

—  Amino acids are classified by various ways.

1. Nutritional Classification

1. Essential amino acid :-

—    There are 8 different types of essential amino

     acid.

—  They are, [MPILLToTeaV].

—    Methionine 

—    Phenylalenine

—    Isoleucine

—    Leucine

—    Lysine

—    Threonine

    

◦       Tryptophan

◦        Valine  

◦       B. Semi essential amino acid

◦            Eg. Arginine & Histidine

◦       C. Non –Essential amino acids

◦           Eg. All the remaining amino acids

II. Classification based on the properties of the

     side chain [R-group], particularly  in their

     polarity or tendency to interact with water

     at Biological P^H (nearly at 7.0 )

—  Based on the polarity of the side chain, amino

   acids are classified into 5 different types.

◦       They are:-

◦       Amino  acid having non-polar aliphatic side chain.

◦       Amino acid having Aromatic side chain.

◦       Amino acid having uncharged (neutral)or non-Ionic polar side chain.

◦       Amino acid having negatively charged side chain.

◦       Amino acid having positively charged side chain.

◦          
Amino acid having non-polar aliphatic side chain 

◦          1.  Glycine

◦           2.  Alanine

◦           3.  Proline

◦           4.  Valine

◦           5.  Leucine

◦           6.  Isoleucine

◦           7.  Methionine                                                  

◦                                                                              

◦          Amino acid having Aromatic side chain

◦           1.   Phenylalanine

◦           2.   Tyrosine

◦           3.   Tryptophan

◦          

◦            Amino acid having uncharged (neutral)

◦             or non-Ionic polar side chain

◦          1.    Serine

◦          2.   Threonine

◦          3.   Cysteine

◦          4.   Asparagine

◦          5.   Glutamine

◦          Amino acid having negatively charged side chain

◦            

◦            1.    Aspertate

◦            2.    Glutamate

◦          Amino acid having positively charged side chain

◦             1.     Arginine

◦              2.    Lysine

◦              3.   Histidine

III. Classification based on the no. of the functional groups.

1. Monoamino  monocarboxylic acid

    Eg. Simple amino acid, Hydroxy amino acid, Branched chain amino acid, Aromatic amino acid, Methionine etc.

B. Monoamino  Dicarboxylic acid

     Eg. Aspertate, Glutamate

C. Diamino  monocarboxylic acid

      Eg. lysine

D. Diamino  Dicarboxylic acid

     Eg. cystine

E. Imino acid

    Eg. proline

4. Classification based on their reaction in

       the solution

1. Neutral amino acid

—  Largest group of amino acid & has been sub classified into 5 different types.

1. Aliphatic amino acid

        —   Simple amino acid :- Glycine, Alanine,

        —   Branched chain amino acid :- Valine, Leucine, Isoleucine.

—  Hydroxy amino acid :- Serine, Threoine

2. Aromatic amino acid :- Phenylalanine, tyrosine
3.  Heterocyclic amino acid :- Tyrosine, Tryptophan.

4. Imino acid  :- Proline, Hydroxy proline
5. Sulfur containing amino acid :- Cysteine, cystine & methionine      

b.  Acidic amino acid &their amide

–   Aspertate, Glutamate,

–   Asparagine & Glutamine

c. Basic amino acid

–   Lysine, Arginine & Histidine

5. Classification based on the Metabolic point

        of view.

—  They are :

1. Purely ketogenic

  Eg. Leucine

II.   Glucogenic & ketogenic

Eg. Phenylalanine, tyrosine & tryptophan

III.  Purely glucogenic

Eg. All the remaining amino acid.