title: Induction of phenylalanine ammonia-lyase activity by tryptophan in Ustilago maydis.
abstract: To understand the regulation of phenylalanine ammonia-lyase (PAL) activity in the corn smut fungus, Ustilago maydis, we examined the effects of different media, metabolic effectors (including aromatic amino acids), and environmental factors on induction and repression of PAL activity. PAL was detected only in cell extracts and not in the culture medium. U. maydis PAL is constitutively produced at a low level in all media tested but its regulation can be influenced by aromatic amino acids. L-Tryptophan (0.3 mM) induces PAL activity 3- to 5-fold but tryptophan analogs and tryptophan-related metabolites do not. The enzyme is most readily induced during the early stationary phase of growth and the induced activity remains relatively constant during stationary stage. No induction or inhibition of PAL activity was observed as a function of culture temperature, pH or light. PAL induction was repressed by glucose but not by its reaction product, t-cinnamic acid. Induction did not require de novo protein synthesis, suggesting that some form of post-translational protein modification or a metabolic effect may be involved. This study shows that the regulation of U. maydis PAL is very different from the patterns known for plants and other fungi.
authors.affiliation: Forest Products Biotechnology, Department of Wood Science, University of British Columbia, 2424 Main Mall, BC, V6T 1Z4, Vancouver, Canada.
authors.forename: S H
authors.initials: SH
authors.lastname: Kim
authors.forename: J W
authors.initials: JW
authors.lastname: Kronstad
authors.forename: B E
authors.initials: BE
authors.lastname: Ellis
mesh_terms: D002244:Carbon / Q000378:metabolism; D003470:Culture Media; D004789:Enzyme Activation; D004790:Enzyme Induction; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008027:Light; D009584:Nitrogen / Q000378:metabolism; D010650:Phenylalanine Ammonia-Lyase / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000378:metabolism; D014364:Tryptophan / Q000494:pharmacology*; D014588:Ustilago / Q000201:enzymology*
chemical_list: D003470:Culture Media; D004791:Enzyme Inhibitors; D002244:Carbon; D014364:Tryptophan; D010650:Phenylalanine Ammonia-Lyase; D009584:Nitrogen