title: Regulation of L-phenylalanine ammonia-lyase from Rhizoctonia solani.
abstract: Maximal levels of L-henylalanine ammonia-lyase activity were observed when the mycelial felts of Rhizoctonia solani were grown for 4.5 days on Byrde synthetic medium containing 3.5% glucose and 0.3% L-phenylalanine, Differential centrifugation studies have indicated that the enzyme is localized in the soluble fraction. The time course of induction of L-phenylalanine ammonia-lyase activity by L-phenylalanine showed a lag period of 1 to 1.5 h and reached a maximum around 4 to 6 h after the addition of the inducer to the medium. L-Phenylalanine, L-tyrosine, and L-tryptophan were nearly equally efficient inducers of the enzyme. D-Phenylalanine was as efficient as the L-isomer, whereas D-tyrosine was a poor inducer. Light, gibberellic acid, indole 3-acetic acid, and kinetin had no effect on the induction of L-phenylalanine ammonia-lyase activity. Cycloheximide did not inhibit the uptake of amino acids by the mycelia but completely blocked the incorporation of radioactive amino acids into soluble proteins and the development of L-phenylalanine ammonia-lyase activity. Actinomycin D inhibited both the incorporation of 32P into ribonucleic acid and the enzyme activity. Conclusive evidence for de novo synthesis of L-phenylalanine ammonia-lyase was obtained by the incorporation of radioactive amino acids into the enzyme. Electrophoretic analysis of the purified preparation showed a single protein band that coincided with radioactivity and L-phenylalanine ammonia-lyase activity. Glucose and intermediates of the tricarboxylic acid cycle, like citric acid, alpha-ketoglutaric acid, and succinic acid, and the metabolites of L-phenylalanine, like o-coumaric acid, o-hydroxyphenylacetic acid, and protocatechuic acid, significantly repressed L-phenylalanine ammonia-lyase activity. The observed repression was not relieved by cyclic adenosine 5'-triphosphate.
mesh_terms: D000642:Ammonia-Lyases / Q000378:metabolism*; D002474:Cell-Free System; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D004790:Enzyme Induction; D004794:Enzyme Repression; D005947:Glucose / Q000378:metabolism; D008027:Light; D003904:Mitosporic Fungi / Q000201:enzymology*; D010649:Phenylalanine / Q000378:metabolism; D010650:Phenylalanine Ammonia-Lyase / Q000378:metabolism*; D010937:Plant Growth Regulators / Q000494:pharmacology; D012232:Rhizoctonia / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism; D013237:Stereoisomerism; D013696:Temperature; D014364:Tryptophan / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
chemical_list: D010937:Plant Growth Regulators; D003609:Dactinomycin; D014443:Tyrosine; D010649:Phenylalanine; D014364:Tryptophan; D003513:Cycloheximide; D000642:Ammonia-Lyases; D010650:Phenylalanine Ammonia-Lyase; D005947:Glucose