title: Activity of L-phenylalanine ammonia-lyase in organic solvents.
abstract: L-Phenylalanine ammonia-lyase (EC 4.3.1.5), (PAL) was shown to be active in a monophasic non-aqueous medium for the first time. Ultraviolet absorbance spectra of trans-cinnamic acid were shown to be similar in both water and n-octanol. High catalytic rates were observed only when the enzyme was placed in solvents containing high concentrations of water. PAL forward reaction was observed only when the water concentration in n-octanol exceeded 2.0% (v/v), which corresponds to a value of 0.8 in thermodynamic water activity (aw) terms. In n-octanol containing either 2.0 or 3.5% (v/v) H2O (and 2 mM L-phenylalanine), lyophilized and aw = 0.113 pre-equilibrated PAL powder exhibited catalytic rates 0.02 and 1.75% of the value observed in aqueous solution respectively. A freshly lyophilized (non-equilibrated) PAL preparation incubated in water-saturated n-octanol (measured [H2O] = 3.6% (v/v), L-phenylalanine concentration approximately 6.8 mM) gave catalytic activity values 17% of those observed in aqueous solution. This is the first demonstration of catalytic activity of an amino acid ammonia-lyase in monophasic organic solvent.
authors.affiliation: Molecular Biology Research Group, School of Biological Sciences, University of Wales Swansea, UK.
authors.forename: D G
authors.initials: DG
authors.lastname: Rees
authors.forename: D H
authors.initials: DH
authors.lastname: Jones
mesh_terms: D020003:1-Octanol; D002934:Cinnamates; D007700:Kinetics; D000442:Octanols; D010650:Phenylalanine Ammonia-Lyase / Q000737:chemistry / Q000378:metabolism*; D012997:Solvents; D013056:Spectrophotometry, Ultraviolet; D014867:Water
chemical_list: D002934:Cinnamates; D000442:Octanols; D012997:Solvents; D014867:Water; C029010:cinnamic acid; D010650:Phenylalanine Ammonia-Lyase; D020003:1-Octanol