Crystal structures of cystathionine β-lyase and cystathionine β-lyase like protein from Bacillus cereus ATCC 14579.

Abstract

Cystathionine β-lyase (CBL) and cystathionine β-lyase-like protein (CBLP) are key PLP-dependent enzymes involved in methionine biosynthesis. In Bacillus cereus ATCC 14579 CBL (BcCBL) and CBLP (BcCBLP) catalyze the conversion of cystathionine to homocysteine and pyruvate. In this study, we found that both BcCBL and BcCBLP effectively catalyze cystathionine cleavage, with BcCBLP exhibiting a higher catalytic efficiency (kcat) and low substrate affinity (K_m). We determined their crystal structures in complex with pyridoxal phosphate (PLP). BcCBL, forming a tetramer, aligns with typical CBLs in sulfur amino acid metabolism, while BcCBLP, forming a dimer, resembles the bifunctional MalY enzyme from Escherichia coli, indicating potential additional regulatory roles. These structural and functional insights highlight the distinct roles of BcCBL and BcCBLP in cellular metabolism. This study provides valuable insights into the structural diversity and potential functions of these enzymes, contributing to the broader knowledge of PLP-dependent enzymatic mechanisms.