Five new low-molecular-mass trypsin inhibitors belonging to the RTI/MTI-2 family were identified from white mustard (Sinapis alba L.; MTI-2) seed. Purified MTI-2 consisted of a peptide mixture, displaying Ile or Arg at position 43, Trp or kynurenine (Kyn) at position 44, and C-terminal ragged ends. The occurrence of Ile or Arg at position 43 suggested that MTI-2 inhibitors originated from different genes. The presence of 5-oxo-proline (pyroglutamic acid; 5-oxoPro1) and Kyn44 reflected post-translational processing of the serine proteinase inhibitor. MTI-2 showed approximate to 70% amino-acid identity with low-molecular-mass trypsin inhibitors isolated from oil rape (Brassica napus var. oleifera; RTI-III) seed and with serine proteinase inhibitors mapped in Arabidopsis thaliana chromosome II (ATTI). Furthermore, MTI-2 was homologous to brazzein, the sweet-tasting protein from Pentadiplandra brazzeana Baillon fruit (approximate to 30% amino-acid identity). Although snake-venom toxins showed a low amino-acid identity (< 20%) with MTI-2, RTI-III, and ATTI, some structurally relevant residues were conserved. The disulfide bridge pattern of MTI-2 (Cys5-Cys27, Cys18-Cys31, Cys42-Cys52, and Cys54-Cys57) corresponded to that of RTI-III and of snake-venom toxins, being different from that of brazzein. Therefore, protein similarity might be attributable to the three-dimensional arrangement rather than to the amino-acid sequence. Values of K-a for MTI-2 binding to bovine beta-trypsin (trypsin) and bovine alpha-chymotrypsin were 6.3 x 10(9) M-1 and 2.0 x 10(6) M-1, respectively, at pH 8.0 and 21.0 degrees C. Moreover, values of k(on) for MTI-2 binding to trypsin and of k(off) for the dissociation of the serine proteinase:inhibitor complex were 5.6 x 10(5) M-1.s(-1) and 8.9 x 10(-5) M-1.s(-1), respectively, at pH 8.0 and 21.0 degrees C. Despite the heterogeneity of the purified inhibitor peptide mixture, the inhibition properties of the different MTI-2 inhibitors were indistinguishable.

Ruoppolo, M., Amoresano, A., Pucci, P., Pascarella, S., Polticelli, F., Trovato, M., et al. (2000). Characterization of five new low-molecular-mass trypsin inhibitors from white mustard (Sinapis alba L.) seed RID A-4573-2009. EUROPEAN JOURNAL OF BIOCHEMISTRY, 267(21), 6486-6492 [10.1046/j.1432-1327.2000.01741.x WC Biochemistry & Molecular Biology].

Characterization of five new low-molecular-mass trypsin inhibitors from white mustard (Sinapis alba L.) seed RID A-4573-2009

POLTICELLI, Fabio;
2000-01-01

Abstract

Five new low-molecular-mass trypsin inhibitors belonging to the RTI/MTI-2 family were identified from white mustard (Sinapis alba L.; MTI-2) seed. Purified MTI-2 consisted of a peptide mixture, displaying Ile or Arg at position 43, Trp or kynurenine (Kyn) at position 44, and C-terminal ragged ends. The occurrence of Ile or Arg at position 43 suggested that MTI-2 inhibitors originated from different genes. The presence of 5-oxo-proline (pyroglutamic acid; 5-oxoPro1) and Kyn44 reflected post-translational processing of the serine proteinase inhibitor. MTI-2 showed approximate to 70% amino-acid identity with low-molecular-mass trypsin inhibitors isolated from oil rape (Brassica napus var. oleifera; RTI-III) seed and with serine proteinase inhibitors mapped in Arabidopsis thaliana chromosome II (ATTI). Furthermore, MTI-2 was homologous to brazzein, the sweet-tasting protein from Pentadiplandra brazzeana Baillon fruit (approximate to 30% amino-acid identity). Although snake-venom toxins showed a low amino-acid identity (< 20%) with MTI-2, RTI-III, and ATTI, some structurally relevant residues were conserved. The disulfide bridge pattern of MTI-2 (Cys5-Cys27, Cys18-Cys31, Cys42-Cys52, and Cys54-Cys57) corresponded to that of RTI-III and of snake-venom toxins, being different from that of brazzein. Therefore, protein similarity might be attributable to the three-dimensional arrangement rather than to the amino-acid sequence. Values of K-a for MTI-2 binding to bovine beta-trypsin (trypsin) and bovine alpha-chymotrypsin were 6.3 x 10(9) M-1 and 2.0 x 10(6) M-1, respectively, at pH 8.0 and 21.0 degrees C. Moreover, values of k(on) for MTI-2 binding to trypsin and of k(off) for the dissociation of the serine proteinase:inhibitor complex were 5.6 x 10(5) M-1.s(-1) and 8.9 x 10(-5) M-1.s(-1), respectively, at pH 8.0 and 21.0 degrees C. Despite the heterogeneity of the purified inhibitor peptide mixture, the inhibition properties of the different MTI-2 inhibitors were indistinguishable.
2000
Ruoppolo, M., Amoresano, A., Pucci, P., Pascarella, S., Polticelli, F., Trovato, M., et al. (2000). Characterization of five new low-molecular-mass trypsin inhibitors from white mustard (Sinapis alba L.) seed RID A-4573-2009. EUROPEAN JOURNAL OF BIOCHEMISTRY, 267(21), 6486-6492 [10.1046/j.1432-1327.2000.01741.x WC Biochemistry & Molecular Biology].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11590/156421
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