The Properties of Cytochrome Oxidase in Cholate Extracts from Soybean Roots.

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Abstract
A dispersed preparation of cytochrome oxidase has been prepared by adding sodium cholate to particulates isolated from roots of soybean seedlings. By use of (NH4)2SO4 the dis persed extract was fractionated into two parts. Addition of either fraction to a solution containing reduced cytochrome c resulted in rapid oxidation. One fraction, which was obtained by 30% saturation with (NH4)2SO4, catalyzed reduced cytochrome c oxidation at a linear rate for a short period of time and exhibited all the well known properties of cytochrome oxidase. The 2d fraction, obtained by increasing (NH4SO4 saturation to 65%, caused an oxidation of reduced cytochrome c at curvilinear rate, then the reaction quickly ceased. The evidence presented indicates that oxidized cytochrome c or a contaminate in this preparation inhibited the oxidation and therefore is responsible for the inactivation. Also the activity of the 2d fraction was strongly inhibited by Antimycin A but was not appreciably inhibited by NaN3 or CO. These properties are in direct contrast to those exhibited by the 0 to 30% (NH4)2SO4 precipitated fraction. The 0 to 30% (1^4)2804 fraction catalyzed the uptake of oxygen; however, all efforts to demonstrate an oxygen requirement for the 30 to 65% (^4)2804 fraction have failed. Samples of the dispersed extracts were dialyzed and assayed with and without added KC1. Concentrations of KC1 that markedly stimulated particulate preparations had no appreciable effect on the dispersed fractions.