Crystallization and preliminary X-ray diffraction analysis of the active core of human recombinant cystathionine beta-synthase: an enzyme involved invascular disease

Cystathionine beta -synthase (CBS) is a unique heme enzyme that catalyzes a PLP-dependent condensation of serine and homocysteine to give cystathionin e. Deficiency of CBS leads to homocystinuria, an autosomal recessively inhe rited disease of sulfur metabolism. A truncated form of CBS in which the C- terminal amino-acid residues have been deleted has been prepared. The trunc ated CBS subunits form a dimer, in contrast to the full-length subunits whi ch form tetramers and higher oligomers. The truncated CBS yielded crystals diffracting to 2.6 Angstrom which belong to space group P3(1) or P3(2). Thi s is the first comprehensive structural investigation of a PLP and heme-con taining enzyme.