CYTOCHROME OXIDASE IN CORN EMBRYOS

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Abstract
Individual corn kernels were placed on moistened filter paper in Warburg flasks at 37[degree] C. Oxygen uptake of the geminating seed ranged from 25 cu. mm. at the 6th hr. to 184 cu. mm. at the 24th hr. The oxygen uptake was decreased slightly by 0.01 M_diethyldithiocarbamate, unaffected by 0.002 M phenylthiourea, and abolished by 0.001 M cyanide or 0.005 M azide. Homogenates of 1 g. of embryos in 4 ml. 0.1 M phosphate buffer, pH 7, were made from embryos with 10- to 11-mm. roots. In the presence of 0.01 M p-phenylenediamine and 3 x 10-5 M cytochrome c, 0.5 ml. of homogenate exhibited an avg. oxygen uptake of 148 cu. mm./hr. at 37[degree]C. Addition of 0.001 M cyanide or 0.005 M azide, or boiling the homogenate, reduced the uptake to about 23 cu. mm./hr. The homogenates did not catalyze the oxidation of 0.0025 M 3,4-dihydroxyphenyl-L-alanine or 0.003 M p-cresol.

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