Subcellular and developmental changes in distribution of aconitase isoforms in pumpkin cotyledons

✍ Scribed by L. Bellis; M. Hayashi; M. Nishimura; A. Alpi

• Book ID: 104661793
• Publisher: Springer-Verlag
• Year: 1995
• Tongue: English
• Weight: 640 KB
• Volume: 195
• Category: Article
• ISSN: 0032-0935
• DOI: 10.1007/bf00202606

✦ Synopsis

The subcellular localization and developmental changes of aconitase (EC 4.2.1.3) isoforms were studied in pumpkin tissues by anion-exchange chromatography. In etiolated pumpkin cotyledons three aconitase isoforms (denoted Aco I, II, and III, respectively) were found, and the first to be eluted (Aco I) represented the major part of the total aconitase activity in the tissue. Aconitase I gradually disappeared during the greening of cotyledons. In hypocotyls, roots and mature leaves Aco I was barely detectable, though the two other isoforms were present. In pumpkin mitochondria purified by differential or density gradient centrifugation, a high amount of Aco II was present, whereas the other isoforms were detected in low quantities. Since aconitase has never been clearly detected in glyoxysomal fractions, we conclude that the first and the third aconitase isoforms are cytosolic, while the second one represents the mitochondrial aconitase. Moreover, the first aconitase isoform is present in appreciable amounts only in etiolated cotyledons, so that it should represent the aconitase isoform involved in the glyoxylate cycle.