Oxidizes L-gulono-1,4-lactone to L-xylo-hexulonolactone which spontaneously isomerizes to L-ascorbate. Can use both cytochrome c and phenazine methosulfate as exogenous electron acceptors, but molecular oxygen does not serve as a substrate. Is very specific for the L-gulono-1,4-lactone substrate, since it cannot oxidize L-galactono-1,4-lactone, D-glucurono-3,6-lactone, D-glucuronate, D-arabinose, or D-xylose. 2 Fe(III)-[cytochrome c] + L-gulono-1,4-lactone = 2 Fe(II)-[cytochrome c] + 3 H(+) + L-ascorbate Divalent metal cation. Is completely inhibited by EDTA, N-ethylmaleimide, Cu(2+), Zn(2+), and potassium cyanide in vitro. Mg(2+) and Ca(2+) have no effect on the dehydrogenase activity, and 1 mm Mn(2+) slightly inhibit the enzyme (21% inhibition). Optimum pH is 8.0. Optimum temperature is 39 degrees Celsius. Is relatively thermostable since preincubation at 60 degrees Celsius for 5 minutes results in only partial inactivation of the enzyme (53% of control). Cofactor biosynthesis; L-ascorbate biosynthesis. Belongs to the oxygen-dependent FAD-linked oxidoreductase family. In contrast to mammalian L-gulono-1,4-lactone oxidases, the ortholog in M.tuberculosis is not a flavoenzyme.