Open AccessNovel Characteristics of Trypanosoma brucei Guanosine 5'-monophosphate Reductase Distinct from Host Animals
Author(s) -
Tomoaki Bessho,
T. Okada,
Chihiro Kimura,
Takahiro Shinohara,
Ai Tomiyama,
Akira Imamura,
Mitsuru Kuwamura,
Kazuhiko Nishimura,
Ko Fujimori,
Satoshi Shuto,
Osamu Ishibashi,
Bruno Kilunga Kubata,
Takashi Inui
Publication year - 2016
Publication title -
plos neglected tropical diseases
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.99
H-Index - 135
eISSN - 1935-2735
pISSN - 1935-2727
DOI - 10.1371/journal.pntd.0004339
Subject(s) - trypanosoma brucei , biochemistry , inosine monophosphate , guanosine , biology , guanosine monophosphate , purine , imp dehydrogenase , nucleotide , nucleoside , enzyme , medicine , surgery , gene , transplantation , mycophenolic acid
The metabolic pathway of purine nucleotides in parasitic protozoa is a potent drug target for treatment of parasitemia. Guanosine 5’-monophosphate reductase (GMPR), which catalyzes the deamination of guanosine 5’-monophosphate (GMP) to inosine 5’-monophosphate (IMP), plays an important role in the interconversion of purine nucleotides to maintain the intracellular balance of their concentration. However, only a few studies on protozoan GMPR have been reported at present. Herein, we identified the GMPR in Trypanosoma brucei , a causative protozoan parasite of African trypanosomiasis, and found that the GMPR proteins were consistently localized to glycosomes in T . brucei bloodstream forms. We characterized its recombinant protein to investigate the enzymatic differences between GMPRs of T . brucei and its host animals. T . brucei GMPR was distinct in having an insertion of a tandem repeat of the cystathionine β-synthase (CBS) domain, which was absent in mammalian and bacterial GMPRs. The recombinant protein of T . brucei GMPR catalyzed the conversion of GMP to IMP in the presence of NADPH, and showed apparent affinities for both GMP and NADPH different from those of its mammalian counterparts. Interestingly, the addition of monovalent cations such as K + and NH 4 + to the enzymatic reaction increased the GMPR activity of T . brucei , whereas none of the mammalian GMPR’s was affected by these cations. The monophosphate form of the purine nucleoside analog ribavirin inhibited T . brucei GMPR activity, though mammalian GMPRs showed no or only a little inhibition by it. These results suggest that the mechanism of the GMPR reaction in T . brucei is distinct from that in the host organisms. Finally, we demonstrated the inhibitory effect of ribavirin on the proliferation of trypanosomes in a dose-dependent manner, suggesting the availability of ribavirin to develop a new therapeutic agent against African trypanosomiasis.