BODY POOL AND SYNTHESIS OF ASCORBIC-ACID IN ADULT SEA LAMPREY (PETROMYZON-MARINUS) - AN AGNATHAN FISH WITH GULONOLACTONE OXIDASE ACTIVITY

Although many vertebrates can synthesize ascorbic acid (vitamin C), it is still unclear from the evolutionary perspective when the ability t o synthesize the vitamin first appeared in the animal kingdom and how frequently the trait has been lost. We report here ascorbic acid biosy nthesis ability in sea lamprey (Petromyzon marinus) which represent th e most ancient vertebrate lineage examined thus far for presence of gu lonolactone oxidase, the enzyme catalyzing the terminal step in biosyn thesis of vitamin C. This finding supports the view that the ancestors of living vertebrates were not scurvy prone and that the loss of gulo nolactone oxidase activity subsequently occurred several times in vert ebrate phylogeny. Adult sea lamprey allocate significant amounts of as corbic acid to the gonads to guaranty high-quality gametes. Tissue sto res of ascorbate were maintained by de novo synthesis (1.2-1.3 mg of a scorbic acid/300-g sea lamprey per day at 15 degrees C) while sea lamp rey fast during spawning migration. We estimate that the in vivo daily renewal rate of ascorbate is 4-5% of the whole-body ascorbate pool ba sed on measurement of its biosynthesis and concentration in the whole animal.