Fluorescent Probes for Analysis and Imaging of Monoamine Oxidase Activity

Abstract

Monoamine oxidases catalyze the oxidative deamination of dietary amines and amine neurotransmitters, and assist in maintaining the homeostasis of the amine neurotransmitters in the brain. Dysfunctions of these enzymes can cause neurological and behavioral disorders including Parkinson's and Alzheimer's diseases. To understand their physiological roles, efficient assay methods for monoamine oxidases are essential. Reviewed in this Perspective are the recent progress in the development of fluorescent probes for monoamine oxidases and their applications to enzyme assays in cells and tissues. It is evident that still there is strong need for a fluorescent probe with desirable substrate selectivity and photophysical properties to challenge the much unsolved issues associated with the enzymes and the diseases.

Monitoring of Monoamine Oxidases as Biomarkers of Disease and Disorder

“…MAO can be typically classified into two isozymes, MAO‐A and MAO‐B, whose physiological distribution is distinct to each other and show different preferences for their substrates . One physiological function of MAOs is known to oxidize considerable number of biogenic amines, such as dopamine, serotonin, or norepinephrine, to corresponding aldehydes and carboxylic acids, playing a significant role in the adrenergic nervous system . Thus, some physiological disorders are found to be positively correlated with the abnormal activity of MAOs (Table ).…”

“…So far, various analytical methods have been developed to measure the activity and expression of MAOs, mostly in vitro : radiometry, liquid chromatography and mass spectrometry, fluorometric assay, and enzyme‐linked immunosorbent assay (ELISA) . Among them, the fluorescent method using molecular probes has been recently received great attention due to its capability to monitor the activity of MAOs in vivo .…”

Two-Photon Small Molecule Enzymatic Probes

“…The majority of known fluorescence sensing systems for MAOs are based on one-photon fluorophores; − only Ahn and co-workers developed compounds 1a and 1b as TP probes for MAOs, for the first time, by applying the known reaction-based sensing scheme (Figure a) . A few of them are selective for MAO-A/-B, but they have not been well-investigated in central neuron disease models or clinic samples.…”