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Din referat: Amino-acizi naturali

Amino-acizi naturali

Amino-acizii sunt combinatii organice care contin in molecula una sau mai multe grupe amino si una sau mai multe grupe carboxil.

Dupa structura, amino-acizii se impart in doua mari categorii:

1.    Alifatici: unde grupele functionale sunt legate de o catena alifatica, chiar daca in molecula exista un nucleu aromatic.

2.    Aromatici: unde grupele functionale sunt legate de un ciclu aromatic.

Dupa asezarea relativa a grupelor functionale se deosebesc a-amino-acizi, ß-amino-acizi, ?-amino-acizi, etc.

Dintre amino-acizii alifatici, cei mai importanti sunt a-amino-acizi, adica acei amino-acizi care contin grupele functionale legate de acelasi atom de carbon. Se deosebesc mai multe categorii mari de a-amino-acizi alifatici:

1.    monocarboxilici

2.    dicarboxilici

3.    hidroxi-amino-acizi

4.    tioamino-acizi

5.    diamino-acizi

6.    amino-acizi heterociclici

Denumirea   

Prescurtarea   

Formula

Amino-acizi  monocarboxilici

Leucina

(acidul a-aminoizocapronic)   

Leu        CH3—CH—CH2—CH—COOH
                 |                    |
               CH3                 NH2

Izoleucina

(acidul a-amino-ß-metilvalerianic)

   
Ileu        CH3—CH2—CH — CH—COOH
                             |         |
                           CH3      NH2

Fenilalanina

(acidul a-amino-ß-fenil-propionic)
   

Fe     
                    —CH2—CH—COOH
                                     |
                                   NH2


Glicocolul(glicina)

(acidul aminoacetic)
   
Gli        CH2— COOH
       |
     NH2

Alanina

(acidul a-aminopropionic)   

Ala        CH3—CH—COOH
                  |
                NH2

Valina

(acidul a-aminoizovalerianic)   

Val         CH3—CH — CH—COOH
                  |         |
                CH3       NH2

Amino-acizi dicarboxilici

Acidul asparagic

(acidul aminosuccinic)   

Asp         HOOC—CH2—CH—COOH
                                    |
                                  NH2
                                 
Acidul glutamic

(acidul a-aminoglutaric)   

Glu         HOOC—CH2— CH2—CH—COOH
                                               |
                                             NH2

Hidroxi-amino-acizi

Treonina

(acidul a-amino-ß-hidroxibutiric)   

Tr        CH3—CH — CH—COOH
                 |           |
                OH      NH2

Tirosina

(acidul a-amino-ß-hidroxifenil-propionic)   

Ti      
    HO                    —CH2—CH—COOH
                                               |
                                             NH2
Serina

(acidul a-amino-ß-hidroxipropionic)   

Ser         CH2 — CH—COOH
       |         |
      OH     NH2

Tio-amino-acizi

Cistina

(acidul di[a-amino-ß-tiopropionic] )    Ci—S

Ci—S     HOOC—CH—CH2—S—S-- CH2—CH—COOH
                      |                                           |
                 NH2                                     NH2

Metionina

(acidul a-amino-?-metiltiobutiric)   

Met     CH2— CH2—CH—COOH
   |                     |
    S -- CH3          NH2

Cisteina

(acidul a-amino-ß-tiopropionic)   

Cis         CH2 — CH—COOH
       |          |
      SH      NH2

Diamino-acizi

Ornitina

(acidul a, d-diaminovalerianic)   

Or       CH2— CH2—CH2—CH—COOH
     |                                |
   NH2                                        NH2

Lisina

(acidul a, e-diaminocapronic)   

Lis       CH2— CH2—CH2—CH2—CH—COOH
    |                                            |
  NH2                                                         NH2

Amino-acizi heterociclici

Prolina

(acidul pirolidin-a-carboxilic)   

Pro                             H2C— CH2 
                           |         |
                         H2C      CH—COOH
                             \       /
                                NH

Hidroxiprolina

(acidul ß-hidroxipirolidin-a-carboxilic)   

Hipro                  HO—HC — CH2
                               |           |
                        H2C      CH—COOH
                            \       /
                               NH

Histidina

(acidul a-amino-ß-imidazolil-(4)-propionic)

(imidazolil-(4)-alanina)   

His            N — C — CH2— CH—COOH
         ||       ||                        |
       HC     CH                NH2
          \       /
             NH

Triptofanul

(acidul a-amino-ß-indolil-(3)-propionic)

(indolil-(3)-alanina)   

Tri                                     
                          — CH2— CH—COOH
                                             |
                                           NH2