Involved in the degradation of pyridoxine or pyridoxamine (free, phosphate-unbound, forms of vitamin B6). Hydrolyzes 4-pyridoxolactone to 4-pyridoxic acid. Has lower activity toward N-hexanoyl-D,L-homoserine lactone, but is not active toward 5-pyridoxolactone and gamma-butyrolactone. 4-pyridoxolactone + H2O = 4-pyridoxate + H(+) Binds 2 Zn(2+) ions per subunit. Inhibited by Hg(2+). Optimum pH is 7.5. Retains 36% of maximum activity at pH 5.0 and 10% of maximum activity at pH 9.5. Optimum temperature is 60-70 degrees Celsius. Stable for 10 minutes at 50 degrees Celsius or lower, 64% of activity remains following 10 minutes incubation at 55 degrees Celsius and 14% of activity remains following 10 minutes incubation at 60 degrees Celsius. Cofactor degradation; B6 vitamer degradation; 4-pyridoxate from pyridoxal: step 2/2. Homodimer. Belongs to the metallo-beta-lactamase superfamily.