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Updated: Aug 22, 2026

Measurement of Heme Synthesis Levels in Mammalian Cells
Published on: July 9, 2015
Homocysteine increases methionine synthase mRNA level in Caco-2 cells
Sandrine Ortiou1, Jean-Marc Alberto, Jean-Louis Guéant
1Laboratoire de Pathologie Cellulaire et Moléculaire en Nutrition, Equipe INSERM 0014, Faculté de Médecine, Vandoeuvre-les-Nancy, France.
Background:
Methionine synthase (MTR) synthesizes methionine from homocysteine, using cobalamin as a cofactor and 5-methyltetrahydrofolate as a cosubstrate.
Aim:
To determine the influence of homocystine (Hcy, dimer of homocysteine) in the presence of either cobalamin or methionine on the transcription and the activity of methionine synthase in Caco-2, a human adenocarcinoma cell line.
Methods:
Methionine synthase activity and quantification of its mRNA by real-time RT-PCR were determined in cells cultivated under four differents conditions: Hcy with cobalamin (Hcy+ Cbl+), Hcy with methionine (Hcy+Met+), methionine with Cbl (Met+ Cbl+) and methionine only (Met+).
Results:
Activity (nmol/h/mg protein) was maximal in cells cultivated in Hcy+Cbl+ (2.45 +/- 0.35), compared to cells cultivated in Hcy+Met+ (0.18 +/- 0.01, p<0.001), in Met+ Cbl+ (1.60 +/- 0.06, p<0.05), and in Met+ (0.40 +/- 0.05, p<0.001), suggesting an adaptation of the cells to requirement in synthesized methionine. The mRNA level of MTR in Hcy+ Cbl+ and Hcy+Met+ (2.82 +/-0.49 and 3.33 +/- 0.48 AU, respectively ) was about 2.5 / 3.0-fold higher than that in Met+ Cbl+ and in Met+ (1.00 +/-0.13 and 1.20 +/-0.20 AU, respectively, p<0.001).
Conclusion:
Methionine synthase expression of Caco-2 cell is under a transcriptional control influenced by Hcy.
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