Table 3. Comparison of the properties of the enzyme that mediates the final step in ascorbate (or erythroascorbate) biosynthesis across five kingdoms.

Adapted from [41]* with incorporation of data from [24,25]†, [28]‡ and the present study.

Properties	GALDH (plants)*	GLO (mammals)*	ALO (fungi)*	GULDH (bacteria)†	GAL/ALO (trypanosomes)‡
Product	L-Ascorbic acid	L-Ascorbic acid	D-Erythroascorbic acid	L-Ascorbic acid	Substrate-dependent
Cellular compartment	Mitochondria	Microsomes	Mitochondria	N/A	Glycosome
Molecular mass (kDa)	56	51	56–60	61	57 (T. cruzi) 59 (T. brucei)
Cofactor Relative substrate specificity	Non-covalent FMN	Covalent FAD	Covalent FAD	Non-covalent flavin (proposed)	Non-covalent FMN
L-Galactonolactone	100	87	87	0	100 (T. cruzi) 74 (T. brucei)
L-Gulonolactone	0–20	100	24	100	3–9
D-Arabinonolactone	−	−	100	−	96 (T. cruzi) 100 (T. brucei)
Km (preferred substrate)	0.12–3.3 mM	0.066 mM (rat) 0.15 mM (goat)	44.1 mM	5.5 mM	0.16 mM (T. cruzi) 0.05 mM (T. brucei)
Essential thiol groups	Yes	Yes	Yes	Yes	Yes