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

Cystathionine β-synthase (CBS) is a unique heme enzyme that catalyzes a PLP-dependent condensation of serine and homocysteine to give cystathionine. Deficiency of CBS leads to homocystinuria, an autosomal recessively inherited disease of sulfur metabolism. A truncated form of CBS in which the C-terminal amino-acid residues have been deleted has been prepared. The truncated CBS subunits form a dimer, in contrast to the full-length subunits which form tetramers and higher oligomers. The truncated CBS yielded crystals diffracting to 2.6 Å which belong to space group P3₁ or P3₂. This is the first comprehensive structural investigation of a PLP and heme-containing enzyme.