Catalyzes the reversible NAD(+)-dependent oxidative deamination of L-phenylalanine to phenylpyruvate. H2O + L-phenylalanine + NAD(+) = 3-phenylpyruvate + H(+) + NADH + NH4(+) kcat is 74.8 sec(-1) with phenylpyruvate as substrate. kcat is 56.2 sec(-1) with ketoleucine as substrate. kcat is 2.2 sec(-1) with 2-oxo-4-phenylbutyrate as substrate. Thermostable. Has a melting point (Tm) of 85.5 degrees Celsius. Amino-acid biosynthesis; L-phenylalanine biosynthesis; L-phenylalanine from phenylpyruvate (PDH route): step 1/1. This enzyme has been engineered to lead to an amine dehydrogenase able to catalyze the direct asymmetric reductive amination of ketones using ammonia as the sole amino donor. This reaction is a highly desirable transformation for the synthesis of chiral amine intermediates, particularly for the pharmaceuticals industry. Belongs to the Glu/Leu/Phe/Val dehydrogenases family.