The Effect of Zinc on Alkaline Phosphatases”

Zinc has been shown to be an element essential to the life and growth of rats, but as yet there is no clear indication of what its function may be in metabolism. There are several reports of the occurrence of zinc in pure biological compounds. Scott and Fisher (1) have shown zinc to be necessary for the crystallization of insulin, although other metals were also effective. Keilin and Mann (2) report that carbonic anhydrase contains 0.32 per cent zinc. However, it has been well established that this enzyme is inhibited by small amounts of added zinc (Meldrum and Roughton (3), and unpublished data from this laboratory). In connection with the role of this red blood cell enzyme it may be significant that a zinc-porphyrin compound is excreted in the urine of humans (4). A zinc-porphyrin has also been isolated from diptherial toxic broth (5). Foster and Waksman (6) have shown zinc to be essential for the growth and fumaric acid production of Rhizopus nigricans. Recently Holmberg (7) has found that a purified uricase preparation contains 0.13 per cent zinc. In previous work from this laboratory (8, 9) we have been able to find no detectable difference in the carbohydrate metabolism of zinc-deficient rats. However, a disturbance of the nitrogen metabolism was observed. This involved a decreased blood nonprotein nitrogen, a marked delay in the rate of absorption of amino acids fed by mouth, an increase in fecal nitrogen excretion, a decrease in the daily urinary creatinine excretion, and a marked