Novel peptide chemistry in terrestrial animals: natural luciferin analogues from the bioluminescent earthworm Fridericia heliota

The cytosolic aminotransferase VAS1 coordinates aromatic amino acid biosynthesis and metabolism

The aromatic amino acids (AAAs) phenylalanine, tyrosine, and tryptophan are basic protein units and precursors of diverse specialized metabolites that are essential for plant growth. Despite their significance, the mechanisms that regulate AAA homeostasis remain elusive. Here, we identified a cytosolic aromatic aminotransferase, REVERSAL OF SAV3 PHENOTYPE 1 (VAS1), as a suppressor of arogenate dehydrogenase 2 (adh2) in Arabidopsis (Arabidopsis thaliana). Genetic and biochemical analyses determined that VAS1 uses AAAs as amino donors, leading to the formation of 3-carboxyphenylalanine and 3-carboxytyrosine. These pathways represent distinct routes for AAA metabolism that are unique to specific plant species. Furthermore, we show that VAS1 is responsible for cytosolic AAA biosynthesis, and its enzymatic activity can be inhibited by 3-carboxyphenylalanine. These findings provide valuable insights into the crucial role of VAS1 in producing 3-carboxy AAAs, notably via recycling of AAAs in the cytosol, which maintains AAA homeostasis and allows plants to effectively coordinate the complex metabolic and biosynthetic pathways of AAAs.

Luciferins Under Construction: A Review of Known Biosynthetic Pathways

Bioluminescence, or the ability of a living organism to generate visible light, occurs as a result of biochemical reaction where enzyme, known as a luciferase, catalyzes the oxidation of a small-molecule substrate, known as luciferin. This advantageous trait has independently evolved dozens of times, with current estimates ranging from the most conservative 40, based on the biochemical diversity found across bioluminescence systems (Haddock et al., 2010) to 100, taking into account the physiological mechanisms involved in the behavioral control of light production across a wide range of taxa (Davis et al., 2016; Verdes and Gruber, 2017; Bessho-Uehara et al., 2020a; Lau and Oakley, 2021). Chemical structures of ten biochemically unrelated luciferins and several luciferase gene families have been described; however, a full biochemical pathway leading to light emission has been elucidated only for two: bacterial and fungal bioluminescence systems. Although the recent years have been marked by extraordinary discoveries and promising breakthroughs in understanding the molecular basis of multiple bioluminescence systems, the mechanisms of luciferin biosynthesis for many organisms remain almost entirely unknown. This article seeks to provide a succinct overview of currently known luciferins’ biosynthetic pathways.

A QM/MM Study on the Initiation Reaction of Firefly Bioluminescence-Enzymatic Oxidation of Luciferin

Among all bioluminescent organisms, the firefly is the most famous, with a high luminescent efficiency of 41%, which is widely used in the fields of biotechnology, biomedicine and so on. The entire bioluminescence (BL) process involves a series of complicated in-vivo chemical reactions. The BL is initiated by the enzymatic oxidation of luciferin (LH₂). However, the mechanism of the efficient spin-forbidden oxygenation is far from being totally understood. Via MD simulation and QM/MM calculations, this article describes the complete process of oxygenation in real protein. The oxygenation of luciferin is initiated by a single electron transfer from the trivalent anionic LH₂ (L^3-) to O₂ to form ¹[L^•2-…O₂^•-]; the entire reaction is carried out along the ground-state potential energy surface to produce the dioxetanone (FDO^-) via three transition states and two intermediates. The low energy barriers of the oxygenation reaction and biradical annihilation involved in the reaction explain this spin-forbidden reaction with high efficiency. This study is helpful for understanding the BL initiation of fireflies and the other oxygen-dependent bioluminescent organisms.

Low-Molecular-Weight Components of Luminescent Reaction of the Siberian Enchytraeid Henlea sp

The first results of the study of chromatographic and spectral properties of the detected lowmolecular-weight activators, putative emitters in the luminescent reaction of Siberian enchytraeid Henlea sp., are presented.

Progress in the Study of Bioluminescent Earthworms

Even though bioluminescent oligochaetes rarely catch people's eyes due to their secretive lifestyle, glowing earthworms sighting reports have come from different areas on all continents except Antarctica. A major breakthrough in the research of earthworm bioluminescence occurred in the 1960s with the studies of the North American Diplocardia longa. Comparative studies conducted on 13 earthworm species belonging to six genera showed that N-isovaleryl-3-aminopropanal (Diplocardia luciferin) is the common substrate for bioluminescence in all examined species, while luciferases appeared to be responsible for the color of bioluminescence. The second momentous change in the situation has occurred with the discovery in Siberia (Russia) of two unknown luminous enchytraeids. The two bioluminescent systems belong to different types, have different spectral characteristics and localization, and different temperature and pH optima. They are unique, and this fact is confirmed by the negative results of all possible cross-reactions. The bioluminescent system of Henlea sp. comprises four essential components: luciferase, luciferin, oxygen and calcium ion. For Friderica heliota, the luminescent reaction requires five components: luciferase, luciferin, ATP, magnesium ion and oxygen. Along with luciferin, more than a dozen analogues were isolated from worm biomass. These novel peptide-like natural compounds represent an unprecedented chemistry found in terrestrial organisms.

Mechanistic investigations of the 2-coumaranone chemiluminescence

In a combinational approach of experimental and theoretical methods, the chemiluminescence mechanism of the 2-coumaranones is investigated into detail.

A Tale Of Two Luciferins: Fungal and Earthworm New Bioluminescent Systems

Bioluminescence, the ability of a living organism to produce light through a chemical reaction, is one of Nature's most amazing phenomena widely spread among marine and terrestrial species. There are various different mechanisms underlying the emission of "cold light", but all involve a small molecule, luciferin, that provides energy for light-generation upon oxidation, and a protein, luciferase, that catalyzes the reaction. Different species often use different proteins and substrates in the process, which suggests that the ability to produce light evolved independently several times throughout evolution. Currently, it is estimated that there are more than 30 different mechanisms of bioluminescence. Even though the chemical foundation underlying the bioluminescence phenomenon is by now generally understood, only a handful of luciferins have been isolated and characterized. Today, the known bioluminescence reactions are used as indispensable analytical tools in various fields of science and technology. A pressing need for new bioluminescent analytical techniques with a wider range of practical applications stimulates the search and chemical studies of new bioluminescent systems. In the past few years two such systems were unraveled: those of the earthworms Fridericia heliota and the higher fungi. The luciferins of these two systems do not share structural similarity with the previously known ones. This Account will survey structure elucidation of the novel luciferins and identification of their mechanisms of action. Fridericia luciferin is a key component of a novel ATP-dependent bioluminescence system. Structural studies were performed on 0.005 mg of natural substance and revealed its unusual extensively modified peptidic nature. Elucidation of Fridericia oxyluciferin revealed that oxidative decarboxylation of a lysine fragment of luciferin supplies energy for light generation, while a fluorescent CompX moiety remains intact and serves as a light emitter. Along with luciferin, a number of its natural analogs were found in the extracts of worm biomass. They occurred to be highly unusual modified peptides comprising a set of amino acids, including threonine, aminobutyric acid, homoarginine, unsymmetrical N,N-dimethylarginine and extensively modified tyrosine. These natural compounds represent a unique peptide chemistry found in terrestrial animals and raise novel questions concerning their biosynthetic origin. Also in this Account we discuss identification of the luciferin of higher fungi 3-hydroxyhispidin which is biosynthesized by oxidation of the precursor hispidin, a known fungal and plant secondary metabolite. Furthermore, it was shown that 3-hydroxyhispidin leads to bioluminescence in extracts from four diverse genera of luminous fungi, thus suggesting a common biochemical mechanism for fungal bioluminescence.