Stimulation of the glyoxylate shunt in gamma-irradiated banana

Surendranathan, K.K.

doi:10.1016/s0031-9422(00)86825-9

Cited by 15 publications

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“…These and other enzymes of the cycle are localized within specialized peroxisomes called glyoxysomes (3). The only reported occurrence of malate synthase and isocitrate lyase activities in a higher plant tissue not involved in lipid to carbohydrate conversion is in ripening fruits (2,32) where these enzymes are thought to be involved with organic acid intercon-'Supported by National Science Foundation Grant PCM 7823156. 2Present address: Department of Biology, Queens University, Kingston, Ontario K7L 3N6.…”

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Role of Malate Synthase in Citric Acid Synthesis by Maturing Cotton Embryos: A Proposal

Miernyk¹,

Trelease²

1981

Plant Physiol.

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Cotton embryos from 34 to 54 days after anthesis were analyzed for organic acids, and enzymes associated with organic acid metabolism. During this developmental period, embryos accumulated citrate. Malate synthase activity appeared at 46 days after anthesis and increased rapidly to 54 days. Of other enzymes examined, only citrate synthase activity increased during this period. As isocitrate lyase activity was absent from cotton embryos during maturation, an 3 To whom reprint requests should be addressed.versions (32). The glyoxylate cycle also is operative as an anaplerotic pathway in microorganisms grown on alkanes or C2 carbon sources (22). There have been several reports of malate synthase without accompanying isocitrate lyase activity in microorganisms (18, 28). In Rhizobia, Stovall and Cole (31) proposed a role for malate synthase in organic acid metabolism.In contrast to the enormous body of knowledge that exists concerning seed germination, relatively little is known about seed development (12). Choinski and Trelease (8) reported that developing cotton embryos synthesized catalase-containing peroxisomes beginning about 22 DAA.4 Malate synthase activity developed just prior to desiccation (46 DAA) and coequilibrated with catalase activity in the peroxisome region of sucrose-density gradients. Isocitrate lyase activity has not been detected at any time during cotton embryo development (8,12,25,33). It now appears that malate synthase, in the absence of detectable isocitrate lyase activity, occurs universally among ungerminated oilseeds (25). The purpose of this investigation was to test for in vivo malate synthase activity and for the possible involvement of malate synthase in organic acid metabolism during the late stages of cotton embryo development. MATERIALS AND METHODSEmbryos. Continuously flowering cotton (Gossypium hirsutum L. cv. Deltapine 61) plants were glasshouse grown at a 12-h 35/25 C thermoperiod and irrigated with one-fourth strength Hoagland solution. Flowers were tagged on the day of anthesis, and developing seeds were selected according to their chronological age, fresh weight, and degree of seed coat sclerification ( Fig. 1) (8).Reagents. Substrates and coupling enzymes were purchased from Sigma. The lithium salt of CoA was purchased from P-L Biochemicals and used to prepare acetyl-CoA as previously described (26

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“…versions (32). The glyoxylate cycle also is operative as an anaplerotic pathway in microorganisms grown on alkanes or C2 carbon sources (22).…”

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confidence: 99%