Kinetic properties of sheep brain glutathione reductase.

The kinetic properties of sheep brain glutathione reductase (GSSGR) were investigated. The enzyme showed Ping-Pong kinetics with double substrate inhibition in the forward direction. Km values for NADPH and GSSG were found to be 60.9 and 116.9 mumol/l, and Ki values were found to be 42.1 and 347.3 mumol/l, respectively. NADP+ inhibition at low fixed concentration of NADPH was mixed-type with a Ki of 281.5 mumol/l and alpha of 0.048. It is concluded that the enzyme shows a hybrid Ping-Pong-ordered branched mechanism.