[In vitro demethylation with a NADPH-generating system containing rat cytosol enzymes]

The author uses during demethylization in vitro two types of NADPH-generating systems: 1) postmitochondrial supernatant, whose disadvantage is that in vivo effects the cause for changes in demethylization could be due both to microsomes and dehydrogenases: 2) imported purified enzymic preparations, which is connected with supplying difficulties. The author proposes the usage of postmicrosomal supernatant (cytosol) from rats' liver to overcome these disadvantages. This fraction is with very good efficiency compared with that of the imported purified enzymes. The isolated cytosol, preserved at -10 degrees keeps its initial activity for a period of three days, but after or six days the diminition of the enzymic activity could be compensated by using simultaneously two substrates-isocytrate and glucose-6-phosphate for demethylizating systems.