| Autor: |
FOLLMER, Cristian, BARCELLOS, Grace B. S., ZINGALI, Russolina B., MACHADO, Olga L. T., ALVES, Elias W., BARJA-FIDALGO, Christina, GUIMARÃES, Jorge A., CARLINI, Célia R. |
| Zdroj: |
Biochemical Journal; November 2001, Vol. 360 Issue: 1 p217-224, 8p |
| Abstrakt: |
Canatoxin is a toxic protein from Canavalia ensiformis seeds, lethal to mice (LD50 = 2mg/kg) and insects. Further characterization of canatoxin showed that its main native form (184kDa) is a non-covalently linked dimer of a 95kDa polypeptide containing zinc and nickel. Partial sequencing of internal peptides indicated homology with urease (EC 3.5.1.5) from the same seed. Canatoxin has approx. 30% of urease's activity for urea, and Km of 2–7mM. The proteins differ in their affinities for metal ions and were separated by affinity chromatography on a Zn2+ matrix. Similar to canatoxin, urease activates blood platelets and interacts with glycoconjugates. In contrast with canatoxin, no lethality was seen in mice injected with urease (10mg/kg). Pretreatment with p-hydroxymercuribenzoate irreversibly abolished the ureolytic activity of both proteins. On the other hand, p-hydroxymercuribenzoate-treated canatoxin was still lethal to mice, and both treated proteins were fully active in promoting platelet aggregation and binding to glycoconjugates. Taken together, our data indicate that canatoxin is a variant form of urease. Moreover, we show for the first time that these proteins display several biological effects that are unrelated to their enzymic activity for urea. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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