2989268756ENSG00000234770ENSMUSG00000034450naP58710n/aNM_178747n/aNP_848862L-Gulonolactone oxidase (EC 1.1.3.8) is an enzyme that produces vitamin C. It is expressed in most mammals, but is non-functional in Haplorrhini (a suborder of primates, including humans), in some bats, and in guinea pigs.

The haplorhine ("simple-nosed") primates, which cannot make vitamin C enzymatically, include the tarsiers and the simians (apes, monkeys and humans).

The strepsirrhine ("bent-nosed" or "wet-nosed") primates, which can still make vitamin C enzymatically, include lorises, galagos, pottos, and, to some extent, lemurs.

[10] L-Gulonolactone oxidase deficiency has been called "hypoascorbemia"[11] and is described by OMIM (Online Mendelian Inheritance in Man)[12] as "a public inborn error of metabolism", as it affects all humans.

[17] Johnson et al. have hypothesized that the mutation of the GULOP pseudogene so that it stopped producing GULO may have been of benefit to early primates by increasing uric acid levels and enhancing fructose effects on weight gain and fat accumulation.

Elevating vitamin C content by overexpressing inositol oxygenase and gulono-1,4-lactone oxidase in A. thaliana leads to enhanced biomass and tolerance to abiotic stresses.

[27][28] L-gulonolactone oxidase (GULO) is an enzyme that helps catalyze the production of ascorbic acid aka vitamin C. Mammals such as humans and guinea pigs do not express this gene due to multiple mutations in a specific exon.

[29] The amino acid sequence of this protein has suggested that rat L-Gulonolactone oxidase is located in the membrane portion of the endoplasmic reticulum due to its multiple B-sheet structure which contains hydrophobic areas.

[32] All these aldonolactone oxidoreductases play a role in some form of vitamin C synthesis, and some (including GULO and ALO) accept substrates of other members.