Intracellular localization and co-factor requirement of amphetamine-tetrazolium reductase of guinea-pig brain.

Abstract Amphetamine dehydrogenase of guinea-pig brain is localized in the crude mitochondrial fraction and for full activity supplementation with soluble supernatant fraction or extra added NADP are necessary. The co-factor present in the supernatant fraction is heat-stable and dialysable. The pH-activity curve of the crude mitochondrial system showed two maxima, the peak in the alkaline region being more elevated than that observed at pH 7.0. Optimal concentrations of NTC and NADP were found to be 0.5 mg/ml and 200–300 μg/ml of the reaction mixture respectively and higher NTC concentration inhibited the enzyme activity slightly whereas any further increase in NADP concentration showed no further increase in diformazan production. K m values for d -amphetamine and NADP under the present experimental conditions were found to be 1.66 × 10 −3 M and 1.33 × 10 −4 M respectively. Thecrude mitochondrial enzyme was found to be inhibited by KCN in the presence of supernatant or NADP, the inhibition by KCN being reversed by dialysis or increasing the amount of NADP. The enzyme activity was also inhibited by metal chelating agents like EDTA, o -phenanthroline, α-α' dipyridyl, 8-hydroxyquinoline, cupferron and dithizone suggesting the possible involvement of a metal ion.