Substrate specificity of the bovine serum amine oxidase and in situ characterisation of aminoaldehydes by NMR spectroscopy

Polyamine-Derived Aminoaldehydes and Acrolein: Cytotoxicity, Reactivity and Analysis of the Induced Protein Modifications

Polyamines participate in the processes of cell growth and development. The degradation branch of their metabolism involves amine oxidases. The oxidation of spermine, spermidine and putrescine releases hydrogen peroxide and the corresponding aminoaldehyde. Polyamine-derived aminoaldehydes have been found to be cytotoxic, and they represent the subject of this review. 3-aminopropanal disrupts the lysosomal membrane and triggers apoptosis or necrosis in the damaged cells. It is implicated in the pathogenesis of cerebral ischemia. Furthermore, 3-aminopropanal yields acrolein through the elimination of ammonia. This reactive aldehyde is also generated by the decomposition of aminoaldehydes produced in the reaction of serum amine oxidase with spermidine or spermine. In addition, acrolein is a common environmental pollutant. It causes covalent modifications of proteins, including carbonylation, the production of Michael-type adducts and cross-linking, and it has been associated with inflammation-related diseases. APAL and acrolein are detoxified by aldehyde dehydrogenases and other mechanisms. High-performance liquid chromatography, immunochemistry and mass spectrometry have been largely used to analyze the presence of polyamine-derived aminoaldehydes and protein modifications elicited by their effect. However, the main and still open challenge is to find clues for discovering clear linkages between aldehyde-induced modifications of specific proteins and the development of various diseases.

Green Oxidation of Heterocyclic Ketones with Oxone in Water

The recently reported efficient conversion of cyclic ketones to lactones by Oxone in neutral buffered water is extended to heterocyclic ketones, namely, cyclic N-Boc azaketones and oxoethers with the aim of obtaining N-protected azalactones and their analogues with oxygen in place of nitrogen. N-Boc-4-piperidinone and all the cyclic oxoethers were successfully oxidized to lactones, while the azacyclic ketones with nitrogen α-positioned to carbonyl were univocally transformed into N-Boc-ω-amino acids and N-Boc-N-formyl-ω-amino acids operating in alkaline water and DMF, respectively.

Insights into polyamine metabolism: homospermidine is double-oxidized in two discrete steps by a single copper-containing amine oxidase in pyrrolizidine alkaloid biosynthesis

Polyamines are important metabolites in plant development and abiotic and biotic stress responses. Copper-containing amine oxidases (CuAOs) are involved in the regulation of polyamine levels in the cell. CuAOs oxidize primary amines to their respective aldehydes and hydrogen peroxide. In plants, aldehydes are intermediates in various biosynthetic pathways of alkaloids. CuAOs are thought to oxidize polyamines at only one of the primary amino groups, a process frequently resulting in monocyclic structures. These oxidases have been postulated to be involved in pyrrolizidine alkaloid (PA) biosynthesis. Here, we describe the identification and characterization of homospermidine oxidase (HSO), a CuAO of Heliotropium indicum (Indian heliotrope), involved in PA biosynthesis. Virus-induced gene silencing of HSO in H. indicum leads to significantly reduced PA levels. By in vitro enzyme assays after transient in planta expression, we show that this enzyme prefers Hspd over other amines. Nuclear magnetic resonance spectroscopy and mass spectrometry analyses of the reaction products demonstrate that HSO oxidizes both primary amino groups of homospermidine (Hspd) to form a bicyclic structure, 1-formylpyrrolizidine. Using tracer feeding, we have further revealed that 1-formylpyrrolizidine is an intermediate in the biosynthesis of PAs. Our study therefore establishes that HSO, a canonical CuAO, catalyzes the second step of PA biosynthesis and provides evidence for an undescribed and unusual mechanism involving two discrete steps of oxidation that might also be involved in the biosynthesis of complex structures in other alkaloidal pathways.

Maize polyamine oxidase in the presence of spermine/spermidine induces the apoptosis of LoVo human colon adenocarcinoma cells

Amine oxidases, which contribute to the regulation of polyamine levels, catalyze the oxidative deamination of polyamines to generate H2O2 and aldehyde(s). In this study, and at least to the best of our knowledge, maize polyamine oxidase (ZmPAO) was used for the first time with the aim of identifying a novel strategy for cancer therapy. The cytotoxicity and the mechanisms of cell death induced by the enzymatic oxidation products of polyamine generated by ZmPAO were investigated. Exogenous spermine and ZmPAO treatment decreased cell viability in a spermine dose‑ and time‑dependent manner, particularly, the viability of the multidrug‑resistant (MDR) colon adenocarcinoma cells, LoVo DX, when compared with drug‑sensitive ones (LoVo WT). Further analyses revealed that H2O2 derived from spermine was mainly responsible for the cytotoxicity. Flow cytometric analysis revealed that treatment with ZmPAO and spermine increased the apoptotic population of LoVo WT and LoVo DX cells. In addition, we found that treatment with ZmPAO and spermine markedly reduced mitochondrial membrane potential in the LoVo DX cells, in agreement with the results of cell viability and apoptosis assays. Transmission electron microscopic observations supported the involvement of mitochondrial depolarization in the apoptotic process. Therefore, the dysregulation of polyamine metabolism in tumor cells may be a potential therapeutic target. In addition, the development of MDR tumor cells is recognized as a major obstacle in cancer therapy. Therefore, the design of a novel therapeutic strategy based on the use of this combination may be taken into account, making this approach attractive mainly in treating MDR cancer patients.