Enzymic and chemical properties of cytoplasmic particles from wheat roots

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Abstract
Roots were separated from wheat which had been germinated for 48 hours under commercial conditions of malting. Cytoplasmic particles were separated from the disintegrated roots by differential centrifuging. Whereas the mitochondria showed a high succinate-cytochrome c reductase activity, none was detected in the microsome fraction. The mitochondrial reduced diphosphopyridine nucleotide-cytochrome c reductase activity was partially (30%) inhibited by antimycin A (3 [mu][image] 370 [mu]g/mg of mitochondrial N), but the similar activity of the microsomes was not inhibited by antimycin A (3 [mu][image] 830 ug/mg of microsomal N). The wheat-root mitochondrial preparation appears to have 2 distinct malonate-sensitive pathways for coupling of oxidation of succinate to reduction of cytochrome c. One pathway is not inhibited by antimycin A, but is particularly labile on storage under oxidative conditions; the other is strongly inhibited by low concentrations of antimycin A, and somewhat less labile on storage. The latter corresponds to the well-known succinic dehydrogenase system of animal tissues. Analyses of lipid, nucleic acid and protein of wheat-root mitochondria and micro-somes are presented. Compared with similar particles from silver-beet petiole, wheat-root microsomes are very rich in ribonucleic acid, and mitochondria from both sources are substantially similar in this respect. Wheat-root microsomes, like those from silver-beet petiole, contain two types of ribonucleic acid as determined by relative resistance to extraction procedures. Comparison of the results for rapidly growing wheat roots with those for relatively dormant beet petioles indicate that the ribonucleic acid content of the microsomes, but not of the mitochondria, is correlated with protein synthesis.
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