| Popis: |
A study has been made of the enzyme uricase from the mold Neurospora crassa. It has been shown that the yield of the enzyme can be increased by growth of the mold in the presence of uric acid. It has also been observed that such addition of uric acid to the medium is stimulatory to growth. A procedure has been devised for purification of this enzyme which is not bound to particulate material in the mold and a product has been obtained which has a higher specific activity than that of any uricase previously prepared. Neurospora uricase has been found to differ in some physical properties, such as solubility, and pH optimum, from the uricases prepared from animal sources. However, inhibition and activation experiments have shown that the enzymes from both sources are functionally similar. Results of partial inhibition of uricase by p-chloromercuribenzoate and activation by reducing agents, such as glutathione and sulfide, have been obtained, which indicate involvement of sulfhydryl groups in at least an activating role. A boiled extract of whole Neurospora has been found to contain at least one activating substance, and reasons have been given for believing that this activation is different from that produced by reducing agents. The question of the existence of a uricase cofactor has been discussed. Spectrophotometric evidence has been obtained for the existence of two or more transient intermediates during the course of uric acid oxidation. A product which has an absorption spectrum similar to those observed for one or more of the transient intermediates has been prepared by oxidation of uric acid with alkaline permanganate. The question of whether uricase is a single enzyme or a complex of enzymes has been discussed. |
