Catalyzes the NADPH-dependent reductive condensation between pyruvic acid and the side chain amino group of L-ornithine to form N(5)-(L-1-carboxyethyl)-L-ornithine. To a lesser extent, can also use L-lysine as substrate (yielding N(6)-(L-1-carboxyethyl)-L-lysine) (By similarity). H2O + N(5)-[1(S)-1-carboxyethyl]-L-ornithine + NADP(+) = H(+) + L-ornithine + NADPH + pyruvate Homotetramer. Belongs to the AlaDH/PNT family. CEOS subfamily.