Jackbean, soybean and Bacillus pasteurii ureases

Biological effects unrelated to ureolytic activity

Authors

  • Cristian Follmer,

    1. Department of Biophysics, IB, and Graduate Program in Cellular and Molecular Biology, Center of Biotechnology, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
    Search for more papers by this author
  • Rafael Real-Guerra,

    1. Department of Biophysics, IB, and Graduate Program in Cellular and Molecular Biology, Center of Biotechnology, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
    Search for more papers by this author
  • German E. Wasserman,

    1. Department of Biophysics, IB, and Graduate Program in Cellular and Molecular Biology, Center of Biotechnology, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
    Search for more papers by this author
  • Deiber Olivera-Severo,

    1. Department of Biophysics, IB, and Graduate Program in Cellular and Molecular Biology, Center of Biotechnology, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
    Search for more papers by this author
  • Célia R. Carlini

    1. Department of Biophysics, IB, and Graduate Program in Cellular and Molecular Biology, Center of Biotechnology, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
    Search for more papers by this author

  • Enzyme: urea amidohydrolase (EC 3.5.1.5).

C. R. Carlini, Department of Biophysics, IB, and Graduate Program in Cellular and Molecular Biology, Center of Biotechnology, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil, CEP 91.501-970.
Fax: + 55 51 3316 7003, Tel.: + 55 51 3316 7606,
E-mail: ccarlini@ufrgs.br

Abstract

In this work we compared two plant ureases, jackbean urease (JBU) and embryo-specific soybean urease (SBU) and a bacterial (Bacillus pasteurii) urease, for kinetic parameters and other biological properties described recently for ureases that are independent of the ureolytic activity. The insecticidal effect of ureases was investigated in feeding trials with the cotton sucker bug, Dysdercus peruvianus (Hemiptera) as an insect model. Contrasting with B. pasteurii urease (PBU), both plant ureases presented potent insecticidal activity, with LD50 values of 0.017% (w/w) and 0.052% (w/w) for JBU and SBU, respectively. The insecticidal property of JBU or SBU was not affected by treatment with p-hydroxymercuribenzoate, an irreversible inhibitor of ureolytic activity of both proteins. Also, contrasting with canatoxin – a urease isoform from jackbean seeds that displays a toxic effect in mice (LD50 = 2 mg·kg−1) – no lethality was seen in mice injected intraperitoneally with JBU or SBU (20 mg·kg−1). Similarly to canatoxin, the three enzymes promoted aggregation of blood platelets (EC50 = 400.0 µg·mL−1, 22.2 µg·mL−1, 15.8 µg·mL−1 for BPU, SBU and JBU, respectively). This platelet activating property was also independent of urease activity. Comparison of the kinetic properties indicated that SBU is fivefold less susceptible than JBU to inhibition by acetohydroxamic acid, a chelator of Ni+2 and Zn+2 ions. The ureases also showed different susceptibility to agents that modify cysteine residues, such as p-hydroxymercuribenzoate and p-benzoquinone. Altogether, these data emphasize that biological properties that are independent of ureolytic activity are not restricted to jackbean ureases and that these proteins may have a role in plant defense against insect predators.

Ancillary