Catalyzes the NADP(+)-dependent oxidation of succinate semialdehyde to succinate. It is believed to be the main source of succinate semialdehyde dehydrogenase activity in Mycobacterium (By similarity). H2O + NAD(+) + succinate semialdehyde = 2 H(+) + NADH + succinate H2O + NADP(+) + succinate semialdehyde = 2 H(+) + NADPH + succinate Belongs to the aldehyde dehydrogenase family. Extended N-terminus.