2.5.1.48	cystathionine gamma-synthase	homocysteine and cysteine interconversion	
4.2.1.22	cystathionine beta-synthase	homocysteine and cysteine interconversion	
4.4.1.1	cystathionine gamma-lyase	homocysteine and cysteine interconversion	
4.4.1.13	cysteine-S-conjugate beta-lyase	homocysteine and cysteine interconversion