Different Intracellular Localization of Two Cytochrome P-450 Systems, Ipomeamarone 15-Hydroxylase and Cinnamic Acid 4-Hydroxylase, in Sweet Potato Root Tissue Infected with Ceratocystis fimbriata

Ipomeamarone 15-hydroxylase activity was mainly recovered inthe pellet fraction between centrifugations at 10,000 and 100,000?gfrom a crude extract of Ceratocystis fimbriata-infected sweetpotato root tissue, whereas cinnamic acid 4-hydroxylase activitywas found between centrifugations at 300 and 10,000?g. Whenparticles in the crude extract were fractionated by sucrosedensity gradient centrifugation, the rough-surfaced microsomeswere distributed over a wide density range from 1.09 to 1.14g cm^–3, judging from the distributions of protein, RNAand NADPH-cytochrome c reductase activity. Phosphorylcholine-glyceridetransferase activity was only in the lighter half of the microsomalfraction (density: 1.09–1.11 g cm^–3). Ipomeamarone15-hydroxylase activity was found in heavier half of the microsomalfraction (density: 1.10–1.14 g cm^–3). We proposethat this tissue has two rough-surfaced endoplasmic reticulumspecies, only one of which carries phosphorylcholine-glyceridetransferase, and that the cytochrome P-450 system is localizedon the species lacking the enzyme. Cinnamic acid 4-hydroxylaseactivity was mainly found in a fraction that had densities of1.17–1.19 g cm^–3 and contained vesicular particlesof various sizes. ¹ Present address: Laboratory of Food Hygienics, Faculty ofAgriculture, Kagawa University, Miki-cho, Kida-gun, Kagawa 761-07,Japan. (Received September 6, 1984; Accepted December 27, 1984)