| Cys_Met_Meta_PP | |||||||||
|---|---|---|---|---|---|---|---|---|---|
 cystathionine beta-lyase (cbl) from escherichia coli in complex with n-hydrazinocarbonylmethyl-2-trifluoromethyl-benzamide | |||||||||
| Identifiers | |||||||||
| Symbol | Cys_Met_Meta_PP | ||||||||
| Pfam | PF01053 | ||||||||
| Pfam clan | CL0061 | ||||||||
| InterPro | IPR000277 | ||||||||
| PROSITE | PDOC00677 | ||||||||
| SCOP2 | 1cs1 / SCOPe / SUPFAM | ||||||||
| CDD | cd00614 | ||||||||
| |||||||||
In molecular biology, the Cys/Met metabolism PLP-dependent enzyme family is a family of proteins including enzymes involved in cysteine and methionine metabolism which use PLP (pyridoxal-5'-phosphate) as a cofactor.[1]
PLP is employed as it binds to amino groups and stabilises carbanion intermediates. PLP enzymes exist in their resting state as a Schiff base, the aldehyde group of PLP forming a linkage with the epsilon-amino group of an active site lysine residue on the enzyme. The alpha-amino group of the substrate displaces the lysine epsilon-amino group, in the process forming a new aldimine with the substrate. This aldimine is the common central intermediate for all PLP-catalysed reactions, enzymatic and non-enzymatic.[2]
PLP is the active form of vitamin B6 (pyridoxine or pyridoxal). PLP is a versatile catalyst, acting as a coenzyme in a multitude of reactions, including decarboxylation, deamination and transamination.[3][4][5]
A number of pyridoxal-dependent enzymes involved in the metabolism of cysteine, homocysteine and methionine have been shown to be evolutionary related.[1] These enzymes are tetrameric proteins of about 400 amino-acid residues. Each monomer has an active site, which however requires the N-terminal of another monomer to be completed (salt bridges to phosphate and entrance way). The phosphopyridoxyl group is attached to a lysine residue located in the central section of these enzymes and is stabilised by π-stacking interactions with a tyrosine residue above it.[6]
There are five different structurally related types of PLP enzymes. Members of this family belong to the type I and are:[1]
Note: MetC, metB, metZ are closely related and have fuzzy boundaries so fall under the same NCBI orthologue cluster (COG0626).[1]