Dr. Raúl N. Ondarza 

ondarza@laguna.fmedic.unam.mx

I. Determination of thiol compounds and disulfide reductase enzymes in Entamoeba histolytica

II. ACTION OF DRUGS ON THE CELL PROLIFERATION AND THIOL COMPOUNDS OF PATHOGENIC AMEBAS: Entamoeba histolytica, Acanthamoeba polyphaga and Naegleria gruberi (subsidized by the National Public Health Institute)

III. THIOL COMPOUNDS IN OPPORTUNISTIC PATHOGENIC AMEBAS: Acanthamoeba and Naegleria (subsidized by the National Council for Science and Technology)

OBJECTIVES

• To look for biochemical differences between pathogenic and non-pathogenic amebas and for the compound and enzyme that substitute for glutathione and glutathione reductase in E. histolytica.
• To determine whether the gene for the glutathione reductase of T. cruzi is located in the DNA minicircles of the kinetoplastid.

SUMMARY

Parasitic diseases caused by protozoa like Entamoeba histolytica (amebiasis) are a public health problem in Mexico and in several parts of the world where sanitary conditions are inadequate. This project is based in the fact that E. histolytica does not contain glutathione or the glutathione reductase enzyme to be found in general in most eukaryotes and prokaryotes. This enzyme plays an important role in both the maintenance of the thiol/disulfide equilibrium, generating glutathione reduced from the oxidate, and acts in combination with the glutathione peroxidase necessary for the detoxification of free radicals, hydrogen peroxides and organic peroxides. At present, the mechanism through which this parasite maintains a reduced intracellular environment and releases toxic oxidant substances is unknown. The foregoing justifies the identification of thiol disulfide compounds not yet described in this parasite through HPLC chromatography as well as the search for the disulfide reductase enzyme of the ameba by means of Molecular Biology techniques using oligonucleotides designed for both the reductant catalytic site (characteristic of enzymes, glutathione reductase, trypanothione reductase, mercury reductase, etc.), and for the variable region.

Knowledge of the oxide-reductant system in this parasite will open up possibilities for the design of specific drugs to alter its metabolism and that do not cause damage to the host.

With respect to Trypanosoma cruzi, we have found through serendipity that it has the gene for glutathione reductase as well as the gene for trypanothione reductase established by other researchers from 1984 onwards (Fairlamb, A.H. et al., 1985 Science 227: 1485-1487).

PARTICIPANTS

• Elsa Ma. Tamayo, M.Sc.
• Gerardo Hurtado Sil, B.Sc.
• Eva Hernández. B.Sc.
• Angélica Iturbe, B.Sc.

BIBLIOGRAPHY

• Ondarza, R.N. (1989) Enzyme regulation by biological disulfides, Bio Science Reports : 593-604.
• Cruz L, Morgan D, Ondarza RN. (1995). Brindley's gland exocrine products of Triatoma infestans. Med. and Veterinary Entom. 9.
• Gutiérrez -Martínez A, Ondarza R N. (1996) Kairomone Effect of Extracts from Coffea canephora over Hypothenemus hampei (Coleoptera: Scolytidae). Enviromental Entomology. 25: (1) 96-100.
• Ondarza R N, Tamayo E. and Hernández R. Molecular detection of an unidentified glutathione reductase gene of Trypanosoma cruzi with high homology to the gene of Echerichia coli. J. Mol. Evol. (submitted for publication).
• Ondarza, R.N., Tamayo, E., Hurtado, G., Hernández, E. and Iturbe, A. (1997). Isolation and purification of glutathionyl-spermidina and trypanothione from Entamoeba histolytica. Arch. Med. Research .
• Ondarza, R.N.,Hernandez,E.,Iturbe,A.,Hurtado, G.and Tamayo E. (1999) "Detection by HPLC of a trypanothione synthetase activity in vitro from Entamoeba histolytica". Biotechnology and Applied Biochemistry, 30, 41-45.
•  Ondarza,R.N.,Iturbe, A., Hurtado, G., Tamayo E., Ondarza, M., and Hernandez,E.(1999) "Entamoeba histolytica: a eukaryote with trypanothione metabolism inste glutathione metabolism". Biotechnology and Applied Biochemistry, 30, 47

BOOKS

• Biología Moderna, Siglo XXI eds 1968 (seven editions) and in Editorial Trillas 8th, 9th and 10th ed (1996).
• Biología Molecular: antes y después de la doble hélice. Siglo XXI eds, 1994.
• The chapter: LA BIOLOGIA MOLECULAR EN MEXICO by Ondarza, RN. (1999), pp. 255-292, in Las Ciencias Naturales en Mexico compiled by Arechiga, H. and Beyer, C. and edited by Consejo Nacional para la Cultura y las Artes y el Fondo de Cultura Economica.ISBN 968-165668-7.
  

DISTINCTIONS

• Fellow, John Simon Guggenheim Foundation (1963).
• Doctor Honoris Causa, University of Paris XIII, 1984.
• President and Founder of the Mexican Biochemistry Society (1957).
• President and Founder of the Academy for Scientific Research (1959), now the Mexican Academy of Science.
• On two occasions visiting professor-researcher at the University of California, San Diego at La Jolla. Scripps Institution of Oceanography. (1964) (1982).
• Member of the National Academy of Medicine since (1962)

14/05/98

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