Differential activities of chorismate mutase isozymes in tubers and leaves of Solanum tuberosum L

• Published in: Plant physiology (Bethesda) Vol. 89; no. 2; pp. 472 - 476
• Main Authors: Kuroki, G.W, Conn, E.E
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01-02-1989
• Subjects: Biological and medical sciences; Cell culture techniques; CELLULOSE; CELULOSA; Chromatography; Cyclic amino acids; DESINTOXICANTES; DETOXICANT; Elution; ENVEJECIMIENTO; Enzymes; FENILALANINA; FEUILLE; Fundamental and applied biological sciences. Psychology; Gels; HOJAS; Imidazoles; INHIBIDORES DE ENZIMAS; INHIBITEUR D'ENZYME; ISOENZIMAS; ISOENZYME; Leaves; Metabolism; PHENYLALANINE; Plant physiology and development; Protein metabolism; SOLANUM TUBEROSUM; TRIPTOFANO; TRYPTOPHANE; TUBERCULE; TUBERCULO; Tubers; VIEILLISSEMENT; Enzymatic activity; Isozyme; Solanum tuberosum; Dicotyledones; Angiospermae; Industrial crop; Spermatophyta; Plant leaf; Solanaceae; Chromatography
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.89.2.472

Chromatography on DEAE cellulose equilibrated with Pipes buffer resolved three forms of chorismate mutase (CM) from tubers and leaves of Solanum tuberosum: CM-1A and CM-1B were activated by tryptophan and inhibited by phenylalanine and tyrosine; CM-2 was unaffected by these aromatic amino acids. When compared to freshly excised disc, 3 day old tuber discs demonstrated a 4.5-fold increase in CM-1 activity following wounding. By contrast, CM-2 activity levels were not affected by this treatment. In aged tuber disc the CM-1:CM-2 activity ratio was 9:1. However, in green leaves the CM-1:CM-2 activity ratio was 1:4 suggesting organ specific regulation for the expression of these isozymes. The CM-1 isozymes isolated from both tubers and leaves shared similar native molecular weight values of 55,000, Km values of 40 to 56 micromolar, and inhibition by phenylalanine (110-145 micromolar concentrations required for 50% inhibition) and tyrosine (50-70 micromolar concentratiosn required for 50% inhibition). The resolution of CM-1 into two forms occurred only in the presence of Pipes buffer. When this buffer was replaced with Ace, Bes, imidazole or Tris, only a single peak of CM-1 activity was observed. In these buffers CM-2 eluted as a shoulder on the CM-1 peak. Analytical isoelectric focusing of the CM-1 fraction followed by assay of the gel yielded only one form of CM-1 with an isoelectric point of 5.0. Gel filtration studies with Pipes buffer yielded molecular weights of 60, 000 for both CM-1A and CM-1B indicating these forms are not the result of aggregation. The two forms of CM-1 may be artifacts generated by Pipes buffer