Tropolysin, a New Oligopeptidase from African Trypanosomes
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- 作者：Rory E. Morty ; Istvá ; n Vadá ; sz ; Patrick Bulau ; Vincent Dive ; Vitor Oliveira ; Werner Seeger ; and Luiz Juliano
- 刊名：Biochemistry
- 出版年：2005
- 出版时间：November 8, 2005
- 年：2005
- 卷：44
- 期：44
- 页码：14658 - 14669
- 全文大小：507K
- 年卷期：v.44,no.44(November 8, 2005)
- ISSN：1520-4995
文摘
Oligopeptidases are emerging as important pathogenic factors and therapeutic targets intrypanosome infections. We describe here the purification, cloning, and biochemical analysis of a newoligopeptidase from two pathogenic African trypanosomes. This oligopeptidase, which we have calledtropolysin (encoded by the trn gene), represents an evolutionarily distant member of the M3A subfamilyof metallopeptidases, ancestral to thimet oligopeptidase, neurolysin, and saccharolysin. The trn gene waspresent as a single copy per haploid genome, was expressed in both the mammalian and insect stages ofthe parasite life cycle, and encoded an 84 kDa protein. Both purified and hyperexpressed tropolysinhydrolyzed bradykinin-derived fluorogenic peptide substrates at restricted sites, with an alkaline pHoptimum, and were activated by dithiothreitol and reduced glutathione and by divalent metal cations, inthe order Zn2+ > Co2+ > Mn2+. Under oxidizing conditions, tropolysin reversibly formed inactivemultimers. Tropolysin exhibited a preference for acidic amino acid side chains in P4, hydrophobic sidechains in P3, and hydrophobic or large uncharged side chains in P1, P1', and P3', while the S2' site wasunselective. Highly charged residues were not tolerated in P1'. Tropolysin was responsible for the bulk ofthe kinin-degrading activity in trypanosome lysates, potently (kcat 
119 s-1) inactivated the vasoactivekinins bradykinin and kallidin, and generated angiotensin(1-7) from angiotensin I. This hydrolysis bothabolished the capacity of bradykinin to stimulate the bradykinin B2 receptor and abrogated bradykininprohypotensive properties in vivo, raising the possibility that tropolysin may play a role in the dysregulatedkinin metabolism observed in the plasma of trypanosome-infected hosts.
119 s-1) inactivated the vasoactivekinins bradykinin and kallidin, and generated angiotensin(1-7) from angiotensin I. This hydrolysis bothabolished the capacity of bradykinin to stimulate the bradykinin B2 receptor and abrogated bradykininprohypotensive properties in vivo, raising the possibility that tropolysin may play a role in the dysregulatedkinin metabolism observed in the plasma of trypanosome-infected hosts.