Involved in the nicotine degradation. Catalyzes the cleavage of 6-hydroxy-3-succinoylpyridine (HSP) by incorporation of oxygen at the 3-position to produce to 2,5-dihydroxypyridine (DHP) and succinic semialdehyde. 4-(6-hydroxypyridin-3-yl)-4-oxobutanoate + 2 H(+) + 2 NADH + O2 = 2,5-dihydroxypyridine + H2O + 2 NAD(+) + succinate semialdehyde Binds 1 FAD per subunit. Alkaloid degradation; nicotine degradation. Cells lacking this gene are still able to grow in nicotine medium. The catalytic efficiency of HspA is lower than that of HspB.