Enzymatic Antioxidants Flashcards
How do Mn and CuZn SOD differ?
CuZn - k = 1.6 x 10^9 M-1s-1 (pH 5.3-9.5)
Mn - k = 1.8 x 10^9 M-1s-1 (pH7.8) or 0.33x 10^9 M-1s-1 at pH 10.2.
i.e. Mn more sensitive to alkaline pH.
CuZn inhibited by cyanide
CUZn resistant to heating, proteolytic digestion and detergents.
What does EC CUZN SOD interact with and how?
of the 3 iso forms, B and C have affinity for heparin and heparin sulphate - use their +ve Arg and Lys residues in C terminus to electrostatic ally interact.
What polymorphisms have been recorded in MnSOD?
Val9Ala - in signal peptide - may affect location and transport.
Iso58Thr - decreased thermal stability and enzymatic activity.
Leu60Phe - now sensitive to redox regulation by intracellular thiols.
Outline the structure of catalase.
4 subunits with a ferric haem at the active site.
240,000 daltons.
haem group buried in non-polar pockets 20A from surface.
NADPH bound to each SU at surfca eprovides stabilisation.
What is the role of GPx4?
Phospholipid Glutathione Peroxidase.
Present in cytoplasm, mt, NM, PM.
Reduces hydrogen peroxide, fatty acids and lipid hydroperoxides using GSH cofactor.
In sperm maturation, catalyses oxidation of protein thiol groups in sperm head.
What mechanisms are thought to cause fALS caused by SOD1?
Aberrant redox chemistry –> peroxidase activity.
Peroxide treatment modifies His to 2-oxo-His - releases Cu and inactivates SOD1.
Superoxide reacting with NO –> ONOO- –> nitronium.
Misfolding - inclusion bodies in motor neurons.
what are the different classes of antioxidants?
Agents catalytically removing FRs.
Proteins minimising pro-oxidant availability.
Proteins oxidising ferrous ions.
Low Mr agents.
What are Tf and Lf?
How does iron binding differ?
80 kDa glycoproteins binding ferric iron with high affinity.
Lf better at iron retention at low pH.
What is the role of MT?
Binds 5-7 ions of zinc, Ag, Cu, Cd and Hg due to coordination with thiolate ligands (Cus-S-).
(low Mr - 6500).
