L-homocysteine

1. (6S)-5-methyl-5,6,7,8-tetrahydrofolate + L-homocysteine = (6S)-5,6,7,8-tetrahydrofolate + L-methionine
2. 5-formimidoyltetrahydrofolate + L-glutamate = N-formimidoyl-L-glutamate + (6S)-5,6,7,8-tetrahydrofolate

Catalysed by MTR, FTCD

1. L-homocysteine + H2O = 2-oxobutanoate + hydrogen sulfide + NH4(+) + H(+)
2. 2-oxo-3-sulfanylpropanoate + [thioredoxin]-dithiol = [thioredoxin]-disulfide + hydrogen sulfide + pyruvate + H(+)

Catalysed by CTH, MPST

1. (6S)-5-methyl-5,6,7,8-tetrahydrofolate + L-homocysteine = (6S)-5,6,7,8-tetrahydrofolate + L-methionine
2. transport of methionine and tryptophan (cytosol to extracellular)

Catalysed by MTR, SLC7A5extracellular space, cytosolOne of 4 routes

1. L-homocysteine + H2O = 2-oxobutanoate + hydrogen sulfide + NH4(+) + H(+)
2. thiosulfate + 2 glutathione = glutathione disulfide + hydrogen sulfide + sulfite + 2 H(+)

Catalysed by CTH, TSTD1

1. L-homocysteine + H2O = 2-oxobutanoate + hydrogen sulfide + NH4(+) + H(+)
2. L-threonine = 2-oxobutanoate + NH4(+)

Catalysed by CTH, SDS, SDSL

1. (6S)-5-methyl-5,6,7,8-tetrahydrofolate + L-homocysteine = (6S)-5,6,7,8-tetrahydrofolate + L-methionine
2. transport of alanine and methionine (cytosol to extracellular)

Catalysed by MTR, SLC7A5extracellular space, cytosolOne of 7 routes

1. (6S)-5-methyl-5,6,7,8-tetrahydrofolate + L-homocysteine = (6S)-5,6,7,8-tetrahydrofolate + L-methionine
2. transport of asparagine and methionine (cytosol to extracellular)

Catalysed by MTR, SLC7A5extracellular space, cytosolOne of 3 routes

1. (6S)-5-methyl-5,6,7,8-tetrahydrofolate + L-homocysteine = (6S)-5,6,7,8-tetrahydrofolate + L-methionine
2. transport of methionine and phenylalanine (cytosol to extracellular)

Catalysed by MTR, SLC7A5extracellular space, cytosolOne of 6 routes

1. (6S)-5-methyl-5,6,7,8-tetrahydrofolate + L-homocysteine = (6S)-5,6,7,8-tetrahydrofolate + L-methionine
2. S-methyl-L-methionine + L-homocysteine = 2 L-methionine + H(+)

Catalysed by MTR, BHMT2

1. L-homocysteine + H2O = 2-oxobutanoate + hydrogen sulfide + NH4(+) + H(+)
2. 2-oxobutanoate + L-kynurenine = (2S)-2-aminobutanoate + kynurenate + H2O

Catalysed by CTH, AADAT

1. (6S)-5-methyl-5,6,7,8-tetrahydrofolate + L-homocysteine = (6S)-5,6,7,8-tetrahydrofolate + L-methionine
2. [thioredoxin]-disulfide + L-methionine + H2O = L-methionine (S)-S-oxide + [thioredoxin]-dithiol

Catalysed by MTR, MSRA

1. (6S)-5-methyl-5,6,7,8-tetrahydrofolate + L-homocysteine = (6S)-5,6,7,8-tetrahydrofolate + L-methionine
2. [thioredoxin]-disulfide + L-methionine + H2O = L-methionine (R)-S-oxide + [thioredoxin]-dithiol

Catalysed by MTR, MSRB3, MSRB1, MSRB2

1. L-homocysteine + H2O = 2-oxobutanoate + hydrogen sulfide + NH4(+) + H(+)
2. Sulfide:glutathione,quinone oxidoreductase

Catalysed by CTH, SQORmitochondrial matrixOne of 3 routes

1. L-homocysteine + H2O = 2-oxobutanoate + hydrogen sulfide + NH4(+) + H(+)
2. ubiquinone-10 + hydrogen sulfide + sulfite + 2 H(+) = ubiquinol-10 + thiosulfate

Catalysed by CTH, SQOROne of 2 routes

1. L-homocysteine + H2O = 2-oxobutanoate + hydrogen sulfide + NH4(+) + H(+)
2. 2-oxobutanoate + L-kynurenine = (2S)-2-aminobutanoate + kynurenate + H2O

Catalysed by CTH, AADATOne of 5 routes

1. L-homocysteine + H2O = 2-oxobutanoate + hydrogen sulfide + NH4(+) + H(+)
2. 2-iminobutanoate + H2O = 2-oxobutanoate + NH4(+)

Catalysed by CTH, RIDA

1. (6S)-5-methyl-5,6,7,8-tetrahydrofolate + L-homocysteine = (6S)-5,6,7,8-tetrahydrofolate + L-methionine
2. transport of methionine and tryptophan (cytosol to extracellular)
3. beta-carboline hydrolysis

Catalysed by MTR, SLC7A5extracellular space, cytosol

1. L-homocysteine + L-serine = L,L-cystathionine + H2O
2. N-acetylglutamate synthase (N-acetyl-L-cystathionine)
3. Carnitine O-Palmitoyltransferase

Catalysed by CBS, NAGS and 1 more