S-adenosylmethionine synthesis in Leishmania infantum promastigotes

Methionine adenosyltransferase (MAT), S-adenosylmethionine (AdoMet), and S-adenosylhomocysteine (AdoHcy), have been analysed at different time-points during the growth curve of Leishmania infantum. MAT activity and AdoMet content peaked in the lag and early log phases, whereas higher levels of AdoHcy were found in stationary phase cells. MAT activity of cell extracts displayed hyperbolic kinetics for both its substrates, L-methionine and ATP, with km values of 35 mu M and 5 mM, respectively. MAT has an absolute requirement for divalent cations, and is dependent on sulfydryl protective agents. Unlike other sources, L. infantum MAT activity seems to be transcriptionally regulated, with an accumulation of MAT-mRNA during rapid growth periods of promastigotes. (C) 1999 Academic Press.