The first step of homocysteine conversion to cysteine is catalyzed by cystathionine beta-lyase, which adds a serine molecule to the substrate. The enzyme is a tetramer with two heme molecules as cofactor (Janosik et al. 2001). CBS also utilises pyridoxal 5'-phosphate (PXLP) as cofactor, at the evolutionarily conserved Lys119 residue (Kery et al. 1999). The cystathionine beta-synthase-like protein (CBSL) is thought to function like CBS.
Kery, V, Kraus, JP, Meyer, JD, Manning, MC, Poneleit, L
Gaustadnes, M, Kraus, JP, Kery, V, Maclean, KN, JanosÃk, M
cystathionine beta-synthase activity of PXLP-K119-CBS tetramer [cytosol]
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