ENTRY       EC 4.2.99.9
NAME        O-Succinylhomoserine (thiol)-lyase
            Cystathionine gamma-synthase
CLASS       Lyases
            Carbon-oxygen lyases
            Other carbon-oxygen lyases
SYSNAME     O-Succinyl-L-homoserine succinate-lyase (adding cysteine)
REACTION    O-Succinyl-L-homoserine + L-Cysteine = Cystathionine + Succinate
SUBSTRATE   O-Succinyl-L-homoserine
            L-Cysteine
            Hydrogen sulfide
            Methanethiol
PRODUCT     Cystathionine
            Succinate
            L-Homocysteine
            Methionine
            2-Oxobutanoate
            NH3
COFACTOR    Pyridoxal phosphate
COMMENT     A pyridoxal-phosphate protein. Also reacts with hydrogen sulfide
            and methanethiol as replacing agents, producing homocysteine and
            methionine respectively. In the absence of thiol, can also
            catalyse beta,gamma-elimination to form 2-oxobutanoate,
            succinate and ammonia.
PATHWAY     PATH: MAP00260  Glycine, serine and threonine metabolism
            PATH: MAP00271  Methionine metabolism
            PATH: MAP00272  Cysteine metabolism
            PATH: MAP00450  Selenoamino acid metabolism
            PATH: MAP00920  Sulfur metabolism
MOTIF       PS: PS00868  [DQ]-[LIVM]-x(3)-[STAGC](2)-T-K-[FYW]-[LIVMF]-x-G-H-
                         [SGN]
GENES       ECO: b3939(metB)
            HIN: HI0086(metB)
            HPY: HP0106(metB)
            BSU: yjcI
            SCE: YJR130C(J2063)
DBLINKS     University of Geneva ENZYME DATA BANK: 4.2.99.9
            WIT (What Is There) Metabolic Reconstruction: 4.2.99.9
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