Figure 3.

Methylation enzymes and tissue expression profiles. A) Diagram of methylation-related genes in Hcy metabolism. Twelve methylation enzymes were selected for database mining and expression profile analysis. THF, tetrahydrofuran; CH₂THF, 5-methylenetetrahydrofolate; CH₃THF, 5-methyltetrahydrofolate; NADPH, reduced form of NADP⁺; NADP⁺, nicotinamide adenine dinucleotide phosphate; Met, methionine; Hcy, homocysteine; SAM, S-adenosylmethionine; SAH, S-adenosylhomocysteine; PE, phosphatidylethanolamine; PC, phosphatidylcholine; H3/H4, histone 3/histone 4. Enzyme abbreviations are listed in

Table 1. B) mRNA distribution profiles of methylation enzymes in human tissues. C) mRNA distribution profiles of methylation enzymes in mouse tissues. Expression profiles of 4 of 12 methylation enzymes listed in Table 1 (enzymes 4–7: BHMT, MTHFR, AHCY, and MTR) are omitted because they are included in the Hcy metabolic enzyme group and presented in Fig. 2B, C. Dashed lines are the upper limits of the confidence intervals of the housekeeping genes. Solid bars highlight gene expressions in the liver. Left and right y axes describe REU and REU/mREU, respectively. Enzyme abbreviations are listed in Table 1.