Abstract
Two members of the copper-containing amine oxidase family are physiologically important proteins: (1) Diamine oxidase (hDAO; AOC1) with a preference for diamines is involved in degradation of histamine and (2) Vascular adhesion protein-1 (hVAP-1; AOC3) with a preference for monoamines is a multifunctional cell-surface receptor and an enzyme. hVAP-1-targeted inhibitors are designed to treat inflammatory diseases and cancer, whereas the off-target binding of the designed inhibitors to hDAO might result in adverse drug reactions. The X-ray structures for both human enzymes are solved and provide the basis for computer-aided inhibitor design, which has been reported by several research groups. Although the putative off-target effect of hDAO is less studied, computational methods could be easily utilized to avoid the binding of VAP-1-targeted inhibitors to hDAO. The choice of the model organism for preclinical testing of hVAP-1 inhibitors is not either trivial due to species-specific binding properties of designed inhibitors and different repertoire of copper-containing amine oxidase family members in mammalian species. Thus, the facts that should be considered in hVAP-1-targeted inhibitor design are discussed in light of the applied structural bioinformatics and structural biology approaches.
Highlights
In humans, the copper-containing amine oxidase (CAO) family consists of three proteins [1].Diamine oxidase prefers diamines and is involved in the degradation of histamine [2], while retina-specific amine oxidase is a monoamine oxidase with enzymatic activity in retina [3], and vascular adhesion protein-1 is a multifunctional cell-surface receptor and an enzyme with preference for monoamines [4]
containing amine amine oxidase oxidase (CAO) has revealed a dimeric protein with a deeply buried active site characterized by highly conserved residues and several common features involved in the catalytic reaction, including a topaquinone (TPQ) cofactor and a conserved aspartate residue, as well as three conserved histidine residues that bind the copper ion crucial for the TPQ biogenesis (hVAP-1: [6,7,8,9,10]; hDAO: [11,12,13] (Figure 1A,B)
Three arms that protrude from one monomer to the other one stabilize the tight dimer of human CAOs, where each monomer consists of three domains, namely, D2, D3, and D4 (Figure 1A)
Summary
The copper-containing amine oxidase (CAO) family consists of three proteins [1]. Diamine oxidase (hDAO; AOC1) prefers diamines and is involved in the degradation of histamine [2], while retina-specific amine oxidase (hRAO; AOC2) is a monoamine oxidase with enzymatic activity in retina [3], and vascular adhesion protein-1 (hVAP-1; AOC3) is a multifunctional cell-surface receptor and an enzyme with preference for monoamines [4]. Both hDAO and hVAP-1 are physiologically essential proteins, but little is known about the physiological function of hRAO.
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