Organic Acid Metabolism in Cellular Organelles of Vigna cylindrica (Mitorisasage) Cotyledons |
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Authors: | Kim Kiu Weon; Nagai Koji; Mukaida Hideshi; Tezuka Takafumi; Yamamoto Yukio |
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Institution: | Department of Agronomy, School of Agriculture, Nagoya University Chikusa-Ku, Nagoya 464, Japan |
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Abstract: | In starchy cotyledons of Vigna cylindrica (L.) Skeels (Mitorisasage)during seed germination, the enzymes of the glyoxylate cyclewere located in the matrix of mitochondria. Glyoxysomes wereabsent. The glyoxylate cycle in the mitochondria supplies organicacids to the tricarboxylic acid cycle. In mitochondria, isocitratelyase activity was much higher than malate synthase activity.Part of the glyoxylate thus produced in mitochondria may benonenzymatically converted to formate by H2O2 and the formatethen converted to CO2 by peroxidase or by formic dehydrogenase.The activity of superoxide dismutase, which supplies H2O2, washigher in mitochondria than in peroxisomes. The remaining glyoxylatein mitochondria is possibly converted to glycine by alanine-glyoxylateaminotransferase or transported to peroxisomes which lackedisocitrate lyase activity but had high malate synthase activity.In peroxisomes, glyoxylate may be also produced from urate,as is suggested by the fairly high activities of uricase, allantoinaseand allantoicase. Judging from the enzyme distribution, Vignaperoxisomes should be capable of producing malate, oxalacetate,citrate, isocitrate and a-ketoglutarate.
1Present address: Department of Horticulture, College of Agricultureand Animal Science, Yeugnam University, Gyeongsan 632, Korea. (Received May 27, 1987; Accepted October 7, 1987) |
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