3 research outputs found
Total Synthesis and Biological Activity of the Arachidonic Acid Metabolite Hemiketal E<sub>2</sub>
The
total synthesis of hemiketal E<sub>2</sub> (HKE<sub>2</sub>) has been
accomplished using a goldÂ(I)-mediated cycloisomerization
followed by oxidation of the enol ether product to introduce a unique
keto-hemiketal, the core structure of HKE<sub>2</sub>. Synthetic hemiketal
E<sub>2</sub> reproduced biosynthetically derived HKE<sub>2</sub> in
the inhibition of human platelet aggregation
Rational Design of Novel Pyridinol-Fused Ring Acetaminophen Analogues
Acetaminophen (ApAP) is an electron
donor capable of reducing radicals
generated by redox cycling of hemeproteins. It acts on the prostaglandin
H synthases (cyclooxygenases; COXs) to reduce the protoporphyrin radical
cation in the peroxidase site of the enzyme, thus preventing the intramolecular
electron transfer that generates the Tyr385 radical required for abstraction
of a hydrogen from arachidonic acid to initiate prostaglandin synthesis.
Unrelated to this pharmacological action, metabolism of ApAP by CYPs
yields an iminoquinone electrophile that is responsible for the hepatotoxicity,
which results from high doses of the drug. We synthesized novel heterocyclic
phenols predicted to be electron donors. Two of these inhibited the
oxygenation of arachidonic acid by PGHS-1 and myoglobin and also were
shown to be more metabolically stable and exhibited less direct cytotoxicity
than acetaminophen. They are leading candidates for studies to determine
whether they are free of the metabolism-based hepatotoxicity produced
by acetaminophen
Protein Modification by Adenine Propenal
Base propenals are products of the
reaction of DNA with oxidants
such as peroxynitrite and bleomycin. The most reactive base propenal,
adenine propenal, is mutagenic in Escherichia coli and reacts with DNA to form covalent adducts; however, the reaction
of adenine propenal with protein has not yet been investigated. A
survey of the reaction of adenine propenal with amino acids revealed
that lysine and cysteine form adducts, whereas histidine and arginine
do not. <i>N</i><sup>Δ</sup>-Oxopropenyllysine, a
lysineâlysine cross-link, and <i>S</i>-oxopropenyl
cysteine are the major products. Comprehensive profiling of the reaction
of adenine propenal with human serum albumin and the DNA repair protein,
XPA, revealed that the only stable adduct is <i>N</i><sup>Δ</sup>-oxopropenyllysine. The most reactive sites for modification
in human albumin are K190 and K351. Three sites of modification of
XPA are in the DNA-binding domain, and two sites are subject to regulatory
acetylation. Modification by adenine propenal dramatically reduces
XPAâs ability to bind to a DNA substrate