cofactor coenzyme

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					Cofactors and
 Coenzymes
                Cofactors
• Groups or molecules (other than amino
  acid residues) which are important to
  catalysis
   – Metals
   – Coenzymes
• If tightly bound, it is called a prosthetic
  group
• Enzyme without prosthetic group
  (cofactor)
   – Apoenzyme
• Enzyme with prosthetic group (cofactor)
   – Holoenzyme
    Catalysis by Coenzymes

Some common
  coenzymes Transfers
• Oxidation/Reduction
  – Nicotinamide Adenine   Hydride ion (H-)
    Dinucleotide (NAD+)
  – Flavin Adenine
    Dinucleotide (FAD)     Electrons
    Catalysis by Coenzymes

Some common
  coenzymes               Transfers
• One carbon metabolism
   – Biotin                CO2
   – Tetrahydrofolate      One carbon
                            groups
                          O
                          C   H   to    CH3
    Catalysis by Coenzymes
Some common                 Transfers
  coenzymes
• Acyl groups and others Acyl groups
   – Coenzyme A
                            Acyl groups
   – Lipoic acid
   – Thiamine pyrophosphate
                            Aldehydes
   – Pyridoxal phosphate    Amino groups
                              and amines
   – 5’-Deoxyadenosyl-      Alkyl groups
    cobalamin
Vitamin Derived Coenzymes
          Derived        Deficiency
Coenzyme    from           caus es
N AD     N iacin         Pellag ra

FAD          Riboflav in Derm atit is
             (B2)
Biocytin     Biotin      Seborrhea
                         (skin)
Tetrahyd ro- Folate      Varies
   fola te
 Vitamin Derived Coenzymes
Co enzy m e A    Pa ntot hen at e Fat igu e
                 + ot hers        Irr ita bility

Thiam ine         Thiam in (B  Beriberi
p yrop hosph at e
Py rodox al      Py ridox ine      Varies
phos phate       (B6)
5’-Deoxya den- Vitami n B 12       Per niciou s
os yl cob ala m in                 Ane mia
     Examples of Coenzyme Catalysis
    Uncatalyzed reaction


     H         O                   H       H
                             H
R    C     C
               O         R   C         R   C     H
     NH3
                             NH3
                   CO2                     NH3
Examples of Coenzyme Catalysis
Catalysis with pyridoxal phosphate (Vitamin B6 derivative)
            H         O                       H        O
        R   C     C                      R   C     C
                      O                                O
            NH3                               NH
            +                 H 2O
             O                               HC

             CH                      X                 X

    X                     X
                                     X       N         X
                                             H
    X        N
             H
                          X
                                     Schiff Base
    Examples of Coenzyme Catalysis

         H        O                  H                 H
    R   C     C                 R   C             R    C
                  O
         NH                          NH                NH

        HC                          HC                HC

X                 X         X             X   X             X
                      CO2

                            X       N     X   X        N    X
X       N         X                                    H
        H                           H
Examples of Coenzyme Catalysis

        H              H                H
    R   C          R   C            R   C    NH2
                                        H
        NH             NH                    H
                                H H2O   O
        CH             CH
                                        CH
X            X X            X
                                    X            X


X       N    X X       N    X       X   N        X
        H              H                H
  Examples of Coenzyme Catalysis
Nicotinamide adenine dinucleotide and alcohol dehydrogenase
                            O
                            C
                                NH2
                                                    H       H   O
                                                -
    H2C
              O
                  N
                                      NH2
                                            [H ]                C
                                                                    NH2
                                            N
                                  N
          OH OH                                         N
          O     O
                                      N     N
      O   P O         P O       CH2         H           R
                                  O
          O           O
                                                    NADH
       NAD+                     OH OH
Examples of Coenzyme Catalysis
                      H             Zn2+
   R   N
                      H             O

                  C   O         H   C   CH3

           H 2N

                                        H
             H            NAD       H   C      OH
                                        CH 3