title: 2,4-Dinitrophenylhydrazone formation at the aldehyde derived by periodate cleavage of alpha-amanitin.
abstract: 10(-4) cleavage of alpha-amanitin after the procedure of Wieland & Fahrmeir (1) but without prior protective methylation of the 6'-hydroxyl of the tryptophan residue affords the alpha-amanitin aldehyde in 45% yield. The aldehyde was found to exhibit Ki = 3.0 and 12 microM for Drosophila melanogaster and wheat germ RNA polymerase II, respectively. This value is approximately 100-fold greater than for the parent alpha-amanitin. Treatment of the alpha-amanitin aldehyde with 2,4-dinitrophenylhydrazine in CH3OH, CH3CN, or dimethylsulfoxide yielded three products. Two of these did not contain the 2,4-dinitrophenyl moiety, showed Ki = 3.3 and 0.26 microM for wheat germ RNA polymerase II (alpha-amanitin, Ki = 0.09 microM), and accounted for 30-60% and 3% of the input alpha-amanitin aldehyde, respectively. The alpha-amanitin-2,4 dinitrophenylhydrazone was recovered in less than 10% yield regardless of reaction condition and showed a Ki = 0.26 microM on wheat germ RNA polymerase II. This hydrazone establishes that the amatoxin molecule can be modified in the dihydroxyisoleucine residue without disruption of binding to the RNA polymerase.
mesh_terms: D000447:Aldehydes / Q000138:chemical synthesis*; D000546:Amanitins / Q000138:chemical synthesis*; D000818:Animals; D004331:Drosophila melanogaster / Q000201:enzymology; D006835:Hydrazones; D007700:Kinetics; D010504:Periodic Acid; D010944:Plants / Q000201:enzymology; D012319:RNA Polymerase II / Q000037:antagonists & inhibitors*; D013329:Structure-Activity Relationship; D014908:Triticum / Q000201:enzymology
chemical_list: C001072:2,4-dinitrophenylhydrazone; D000447:Aldehydes; D000546:Amanitins; D006835:Hydrazones; D010504:Periodic Acid; D012319:RNA Polymerase II