L-Gulono-gamma-lactone oxidase (L-gulono-gamma-
lactone:
oxygen 2-
oxidoreductase, EC 1.1.3.8) is the
enzyme that catalyzes the terminal step of
L-ascorbic acid biosynthesis in mammalian liver. The absence of the
oxidase activity in primates and guinea pigs is the reason why these animals are subject to
scurvy, which must be considered an inborn error of metabolism. Attempts were made to determine if a
protein immunologically crossreactive with
L-gulono-gamma-lactone oxidase is present in these animals.
Detergent-solubilized microsomal preparations from guinea pig and African green monkey liver did not precipitate the
antisera directed to either rat or goat
enzyme, nor did any of the other cell fractions obtained from guinea pig liver react with either antiserum. No crossreactive
protein was detectable in guinea pig microsomes even with the sensitive procedure or micro-
complement fixation. On the other hand, extracts of all 10 other mammalian (4 orders) liver microsomes tested were shown to contain
L-gulono-gamma-lactone oxidase activity that did crossreact with
antibodies to the rat and goat
enzymes. One explanation of these findings is that, in the guinea pig, and perhaps in primates too, the structural gene for
L-gulono-gamma-lactone oxidase is not expressed.