L-gulonolactone oxidase

 L -gulonolactone oxidase (EC 1.1.3.8) is an enzyme that catalyzes the reaction of D -glucuronolactone (also known as L -gulono-1,4-lactone) with oxygen to L -xylo-hex-3-ulonolactone and hydrogen peroxide. It uses FAD as a cofactor.

The CAS number for this enzyme is

Gulonolactone oxidase deficiency
The non-functional GULOP was mapped to human chromosome 8p21 that corresponds to an evolutionarily conserved segment on either porcine chromosome 4 (SSC4) or 14 (SSC14). GULO produces ascorbic acid, which is often called "vitamin C".

Animals that have lost the ability to synthesize vitamin C are, notably: simians (primates), guinea pigs, the red-vented bulbul, fruit-eating bats and a species of trout.

Gulonolactone oxidase deficiency is called "hypoascorbemia" and is described by OMIM (Online Mendelian Inheritance in Man) as "a public inborn error of metabolism", as it affects all humans. There exists a wide discrepancy between the amounts of ascorbic acid other primates consume and what is recommended as "reference intakes" for humans.