Structural insights into pathogenic mutations in heme-dependent cystathionine-beta-synthase

Human cystathionine β-synthase plays a key role in maintaining low intracellular levels of homocysteine and is unique in being a pyridoxal phosphate-dependent enzyme that is a hemeprotein. It catalyzes the β-replacement of serine and homocysteine to generate the condensation product, cystathionine. While the structure of a truncated catalytic core of the protein has been determined by crystallography, a model for the full-length enzyme has been developed guided by hydrogen–deuterium exchange mass spectrometric and docking studies. In this review, we have utilized the available structural models for human cystathionine β-synthase to conduct a structure–function analysis of a select group of pathogenic mutations described in patients with hereditary hyperhomocysteinemia.