Flavin-dependent enoate reductase that catalyzes the chemo- and stereoslective hydrogenation of electron-poor alkenes. The enzyme is reduced by NADPH, and oxygen, quinones, and alpha,beta-unsaturated aldehydes and ketones can act as electron acceptors to complete catalytic turnover. The physiological oxidant remains elusive. A + H(+) + NADPH = AH2 + NADP(+) Homodimer or heterodimer. Belongs to the NADH:flavin oxidoreductase/NADH oxidase family.