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The Molecular Mechanism of Intermolecular Signal Transduction in Cystathionine‐β‐Synthase (CBS)
Author(s) -
Chandrasekaran Sita S.,
Ruiz Donovan George,
Kennedy Dana Renae,
Esquerra Raymond M.
Publication year - 2018
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2018.32.1_supplement.796.32
Subject(s) - cystathionine beta synthase , cystathionine gamma lyase , heme , chemistry , cofactor , serine , biochemistry , homocysteine , enzyme , active site , ligand (biochemistry) , homocystinuria , pyridoxal phosphate , stereochemistry , methionine , cysteine , amino acid , receptor
Human cystathionine‐β‐synthase (hCBS) is a pyridoxal phosphate‐dependent (PLP) enzyme that contains heme and catalyzes the β‐replacement reactions of serine (L‐Ser) by homocysteine (L‐Hcy) to produce cystathionine. Mutation in this key mammalian enzyme causes hyperhomocysteinemia, which leads to aggressive arterial diseases, a clinical phenotype observed in patients. Although the role of PLP is similar to other PLP dependent enzymes that catalyze the exchange of the hydroxyl group of serine to thiolate in homocysteine, little is known about the role that heme plays in regulating the catalytic process. My project seeks to develop a continuous, kinetic assay to measure CBS activity. Two approaches are being explored: 1) A coupled kinetic assay, in which the cystathionine produced by CBS is used by Cystathionine‐β‐lyase (hCBL) to generate pyruvate, and pyruvate production is measured phototrically; 2) A novel nuclear magnetic resonance assay, in which we will monitor the direct production of cystathionine over time. These methods will be compared to the standard, but discontinuous, radiometric assay. These assays will be used to understand the effect of small ligand binding to the heme and point mutations at the heme cofactor in relation to the enzyme activity. The long‐term goal of this work is to use time‐resolved absorption and magnetic circular dichroism spectroscopy to understand how small ligand binding to the heme induces conformational changes at the PLP active site in CBS and to measure activity of CBS with various mutated active site residues. Support or Funding Information Arnold and Mabel Beckman Foundation; NIH MARC: T34‐GM008574 This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .