Ma. Carsol et al., A NEW KINETIC-MODEL FOR THE MODE OF ACTION OF SOLUBLE AND MEMBRANE-IMMOBILIZED GLUTATHIONE-PEROXIDASE FROM BOVINE ERYTHROCYTES - EFFECTS OFSELENIUM, European journal of biochemistry, 247(1), 1997, pp. 248-255
Kinetic studies on the oxidative reaction of glutathione by hydrogen p
eroxide were performed using soluble and membrane-bound ox erythrocyte
glutathione peroxidase of various types. The effects of organic and i
norganic selenium on the glutathione peroxidase activity were also exa
mined. The kinetic behaviour of the enzyme was investigated using a co
upled reaction within a relatively large range of hydrogen peroxide an
d glutathione concentrations. Non-parallel double-reciprocal plots wer
e obtained which suggested that a sequential ordered rather than a pin
g-pong mechanism was involved. Similar results were obtained with solu
ble and membrane-bound enzyme, whatever the type of crosslinking used.
Crosslinking was performed on a nylon support using various alkylatin
g agents and bifunctional molecules, With all three types of immobiliz
ed enzyme thus obtained, a slight but significant increase in the k(m)
was observed. The effects of selenium were then studied. Using solubl
e enzyme, a slight increase in the activity was observed in the presen
ce of inorganic selenium (sodium selenite) but not with organic seleni
um (seleno-L-methionine). Inorganic selenium alone was also found to h
ave a slight effect on the membrane-bound enzyme. An increase in the c
atalytic efficiency was observed when glutathione: peroxidase was boun
d using lysine as the bifunctional agent and either glutaraldehyde or
triethyloxonium tetrafluoroborate as the reticulation agent, after a t
hree-month period of incubation.