Development of mechanism-based inhibitors and the related inhibition mechanism study have always been significant studies in the field of copper amine oxidases (CAOs).
In Chapter 2, synthesis of several analogs of 1-amino-2,3-butadiene, which contain mono- or disubstitution at C4, and screening against bovine plasma amine oxidase (BPAO) and Arthrobacter globiformis amine oxidase (AGAO) are described. In the case of AGAO, the crystal structure of the enzyme derivitized with 6-phenylhexa-2,3-dienylamine has been obtained. This structure reveals the covalent attachment of the aldehyde product generated from amine oxidation to the amino group of the reduced TPQ cofactor.
In Chapter 3, evaluation as inhibitor of BPAO of a novel activated allylamine derivative acetic acid-3-amino-propenyl ester is described. Both the E- and Z-isomers display two modes of inactivation of BPAO, reversible and irreversible. In the reversible inactivation pathway, (E)-acetic acid-3-amino-propenyl ester (1) acts as a substrate of BPAO to induce the temporary reversible inactivation of BPAO. A new inactivation mechanism was proposed for the permanent inactivation of BPAO by (E)-acetic acid-3-amino-propenyl ester (1), which involves hydrolysis of product Schiff base at the ester bond followed by tautomerizaiton of TPQ adduct I to II (hydrolysis-tautomerization mechanism).
In Chapter 4, kinetic analyse of propargylamine derivatives 4-phenoxy-2-butynamine (PBA) and 4-(4-methylphenoxy)-2-butynamine (MPBA) as both substrates and inhibitors of BPAO is described. The substrate activity, the inhibitory activity, and the corresponding α-C deuterium isotope effects on both activities were determined for both compounds vs. BPAO. To obtain further insights into the inactivation mechanism, the inactivation of the native BPAO and the substrate-reduced BPAO by the turnover product α, β-unsaturated aldehydes was evaluated. The results can be reconciled by a mechanism where the turnover product α, β-unsaturated aldehyde forms an adduct with the amino group of the reduced TPQ cofactor.
In Chapter 5, synthesis of several Ar-X-extended derivatives of homopropargylamine (X=NH, O) and evaluation of them as BPAO inhibitors are described. The structural basis of inactivation was probed by UV-Vis spectrophotometric studies, mass spectrometry, and immunochemical analysis.