ENTRY       EC 4.2.1.22
NAME        Cystathionine beta-synthase
            Serine sulfhydrase
            beta-Thionase
            Methylcysteine synthase
CLASS       Lyases
            Carbon-oxygen lyases
            Hydro-lyases
SYSNAME     L-Serine hydro-lyase (adding homocysteine)
REACTION    L-Serine + L-Homocysteine = Cystathionine + H2O
SUBSTRATE   L-Serine
            L-Homocysteine
            L-Cysteine
            Cysteine thioether
            beta-Substituted alpha-L-amino acid
PRODUCT     Cystathionine
            H2O
COFACTOR    Pyridoxal phosphate
COMMENT     A pyridoxal-phosphate protein. A multifunctional enzyme: catalyses
            beta-replacement reactions between L-serine, L-cysteine, cysteine
            thioethers or some other beta-substituted alpha-L-amino acids and
            a variety of mercaptans.
PATHWAY     PATH: MAP00260  Glycine, serine and threonine metabolism
            PATH: MAP00271  Methionine metabolism
            PATH: MAP00450  Selenoamino acid metabolism
DISEASE     MIM: 236200  Cystathionine beta-synthase; Homocystinuria,
                         B6-responsive and nonresponsive types (3)
MOTIF       PS: PS00901  K-x-E-x(3)-[PA]-[STAGC]-x-S-[IV]-K-x-R-x-[STAG]-x(2)-M
GENES       SCE: YGR155W(CYS4)
            HSA: CBS(Hs.84152)
DBLINKS     University of Geneva ENZYME DATA BANK: 4.2.1.22
            WIT (What Is There) Metabolic Reconstruction: 4.2.1.22
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