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Inhibition of Urease Activity by Heterocyclic Sulfur Compounds¹

ABSTRACT

The inhibition of both jack bean urease and soil urease by several heterocyclic mercaptans was investigated. The following compounds not previously tested as urease inhibitors were found to be effective inhibitors of jack bean urease: 1,3,4-thiadiazole-2,5-dithiol; 5-mercapto-3-phenyl-1,3,4-thiadiazole-2-thione; and 5-amino-1,3,4-thiadiazole-2-thiol. The disulfides of the latter two compounds were found to be very potent inhibitors of jack bean urease. The results are consistent with an inhibition mechanism involving a thiol-disulfide exchange reaction between a disulfide and one or more of the sulfhydryl groups of urease. The results also imply that inhibition of urease by the heterocyclic mercaptans was due to trace amounts of the corresponding disulfides or polysulfides in the mercaptan preparations. A number of heterocyclic mercaptans, two disulfides, and a number of known urease inhibitors were evaluated as soil urease inhibitors, and the following compounds were the most effective: 1,4-benzoquinone hydroquinone > 2,5-dimethyl-1,4-benzoquinone catechol 1,3,4-thiadiazole-2,5-dithiol 2,6-dimethyl-1,4-benzoquinone.

¹ Publishing of this work and manuscript preparation were supported in part by National Science Foundation Grants DEB-02027 A03 and DEB-02027 A04 to the Grassland Biome, U.S. International Biological Program.

² Graduate Student, Dep. of Soil Science; Professor, Dep. of Soil Science; and Graduate Student, Dep. of Chemistry, Univ. of Alberta, T6G 2E1, Edmonton, Alberta, Canada, respectively.

Current address of senior author is Post-Doctoral Fellow, Natural Resource Ecology Lab., Colorado State Univ., Fort Collins, Co. 80523.

Received for publication May 6, 1977. Accepted for publication September 15, 1977.