Metabolism of trans-Aconitic Acid in Maize

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Abstract
Trans-aconitate synthesis via citrate dehydrase was determined in crude extracts of maize (Z. mays L.) coleoptiles. Two molecular forms of this enzyme were purified by substrate-specific elution from DEAE-cellulose, ammonium sulfate precipitation and gel filtration. Each molecular form migrates as a single band in isoelectric focusing. Gel filtration and sodium dodecyl sulfate electrophoresis provided evidence that 1 enzyme form is composed of 4 80,000-dalton subunits while the other is composed of 2 60,000-dalton subunits. There was no evidence of proteolytic conversion of the large to the small MW form when the former was incubated with either the 15,000 g supernatant or with proteases. The data indicate that the 2 molecular forms of citrate dehydrase are isozymes.