Abstract: Disclosed are methods, systems, components, and compositions for engineering enzymes. Particularly disclosed are methods, systems, components, and compositions for engineering phenylalanine ammonia-lyase (PAL) enzymes and isolating variant PAL enzymes with enhanced enzymatic properties. The variant PAL enzymes disclosed herein or obtained by the methods disclosed herein may be utilized for treating diseases or disorders characterized by elevated blood levels of phenylalanine, such as phenylketonuria (PKU).