Uptake and metabolism of S-adenosyl-L-methionine by Leishmania mexicana and Leishmania braziliensis promastigotes

• Published in: Molecular and biochemical parasitology Vol. 58; no. 1; pp. 123 - 134
• Main Authors: AVILA, J. L, POLEGRE, M. A
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier Science 01.03.1993
• Subjects: Amino Acids - pharmacology; Animals; Biochemistry. Physiology. Immunology. Molecular biology; Biological and medical sciences; Biological Transport - drug effects; Carbohydrates - pharmacology; Fundamental and applied biological sciences. Psychology; Invertebrates; Kinetics; Leishmania braziliensis - drug effects; Leishmania braziliensis - metabolism; Leishmania mexicana - drug effects; Leishmania mexicana - growth & development; Leishmania mexicana - metabolism; Lipids - analysis; Methylation; Morphogenesis; Protozoa; S-Adenosylhomocysteine - metabolism; S-Adenosylmethionine - metabolism; Time Factors; Tropical medicine; Protozoa; Adenosylmethionine; Radiolabelling; Rhizoflagellata; Leishmania brasiliensis; Inhibition; Pathogen; Metabolism; Uptake; Leishmania mexicana
• ISSN: 0166-6851; 1872-9428
• DOI: 10.1016/0166-6851(93)90096-G

Promastigotes of Leishmania mexicana and Leishmania braziliensis incorporate S-adenosyl-L-[3H-methyl]methionine (AdoMet) against a concentration gradient through a saturable system. This concentrative uptake requires metabolic energy and is sensitive to temperature and sulfhydryl reagents such as N-ethyl maleimide. Intracellular AdoMet exchanges with external AdoMet. At steady state, unaltered ADoMet in the intracellular pool is at about a 1800-fold concentration in relation to that found in the external medium. Glucose, galactose and ribose did not stimulate uptake rates. Incorporated AdoMet goes into the soluble AdoMet pool, where a small fraction is metabolized, chiefly into methylthioadenosine, decarboxylated AdoMet and methanol. After a 60 min pulse the radioactivity associated with the [3H]AdoMet incorporated disappears with a half-time of 2 h. Transmethylation reactions were analyzed following [3H]AdoMet incorporation. Fractionation experiments indicate that 45-62% and 30-42% of the radioactivity is incorporated into lipids and protein methyl esters respectively, with 5-14% present in the soluble pool of parasites. Sinefungin or its cyclic derivative (1 and 10 micrograms ml-1) in the incubation medium produces 58% and 64% inhibition of AdoMet incorporation into Leishmania promastigotes. Most transmethylation reactions are inhibited, as there is a 50% decrease in the total radioactivity present in both the base-labile and lipidic fraction, with a parallel increase in the percentage of radioactivity in the soluble pool. Previous results give evidence of the importance of AdoMet in American Leishmania promastigote metabolism.