Mode of action of cystathionine beta-lyase.

Cystathionine beta-lyase (CBL) is a member of the gamma-family of pyridoxal-5'-phosphate (PLP)-dependent enzymes (Alexander et al., 1994) that cleave C(beta,gamma)-S bonds of a broad variety of substrates. Recently, we reported the X-ray crystal structures of CBL and the CBL-trifluoroalanine inactivation complex at 1.83 A and 2.3 A resolution, respectively. The structures explicitly reveal the cofactor and substrate binding pockets. Spectral analysis of substrate turnover indicates a change of hydrophobicity in the microenvironment of the aldimine bond. In combination with further spectroscopic data, crystallographic evidence permits the formulation of a likely reaction mechanism.