. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. UREASE IN SEA URCHIN EGGS 61 In order to have a more complete picture of the role of urease, it would be help- ful to know how urea might be formed in the eggs. There are several pathways of urea formation, of which two are the ornithine cycle and the degradation of purines. Since the presence of a system such as the ornithine cycle, which would manufacture urea at the expense of energy only to have it immediately broken down again, seemed unlikely, it was decided to test for various enzymes of purine degradation. Homog- ena
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. UREASE IN SEA URCHIN EGGS 61 In order to have a more complete picture of the role of urease, it would be help- ful to know how urea might be formed in the eggs. There are several pathways of urea formation, of which two are the ornithine cycle and the degradation of purines. Since the presence of a system such as the ornithine cycle, which would manufacture urea at the expense of energy only to have it immediately broken down again, seemed unlikely, it was decided to test for various enzymes of purine degradation. Homog- enates of unfertilized eggs were examined qualitatively for the presence of adenase, xanthine oxidase, uricase, allantoinase, and allantoicase. Adenase was not demon- strable in more than trace amounts in two independent experiments using the method employed for urease, but with adenine as substrate. Xanthine oxidase was tested for using a modified Thunberg technique with both xanthine and hypoxanthine as substrates. Both substrates gave decolorization times of 10-15 minutes at 29° C. and pH , while in the absence of substrates, decolorization did not occur within 40 minutes. It is concluded that the enzyme is present. Uricase activity was meas- ured in a Warburg apparatus. Two ml. of brei ( ml. packed eggs per 2 ml.), to 100 80 60 LU o: ID 40 20 I T I T. 20 40 60 80 100 UREA CONCENTRATION mg/vial FIGURE 2. The in vivo activity of urease in unfertilized eggs of Strongylocentrotus pnrpuratus as a function of concentration of urea in the sea Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952; Lillie, Frank Rattray, 1870-1947; Moore, Carl Richard, 1892-; Redfield, Alfred Clar
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