Enzymatic activity of albumin shown by coelenterazine chemiluminescence

Abstract

Bioluminescence, the emission of light from live organisms, occurs in 18 phyla and is the major communication system in the deep sea. It has appeared independently many times during evolution but its origins remain unknown. Coelenterazine bioluminescence discovered in luminous jellyfish is the most common chemistry causing bioluminescence in the sea, occurring in seven phyla. Sequence similarities between coelenterazine luciferases and photoproteins from different phyla are poor (often < 5%). The aim of this study was to examine albumin that binds organic substances as a coelenterazine luciferase to test the hypothesis that the evolutionary origin of a bioluminescent protein was the result of the formation of a solvent cage containing just a few key amino acids. The results show for the first time that bovine and human albumin catalysed coelenterazine chemiluminescence consistent with a mono-oxygenase, whereas gelatin and haemoglobin, an oxygen carrier, had very weak activity. Insulin also catalysed coelenterazine chemiluminescence and was increased by Zn(2+). Albumin chemiluminescence was heat denaturable, exhibited saturable substrate characteristics and was inhibited by cations that bound these proteins and by drugs that bind to human albumin drug site I. Molecular modelling confirmed the coelenterazine binding site and identified four basic amino acids: lys195, arg222, his242 and arg257, potentially important in binding and catalysis similar to naturally occurring coelenterazine bioluminescent proteins. These results support the 'solvent cage' hypothesis for the evolutionary origin of enzymatic coelenterazine bioluminescent proteins. They also have important consequences in diseases such as diabetes, gut disorders and food intolerance where a mono-oxygenase could affect cell surface proteins.

An endogenous green fluorescent protein–photoprotein pair in Clytia hemisphaerica eggs shows co-targeting to mitochondria and efficient bioluminescence energy transfer

“…Several distinct families of lucifierases have been characterized and are thought to have arisen independently during evolution [2,11,12]. Aequorin family luciferases are found in cnidarians and ctenophores, although in anthozoan cnidarians their bioluminescence function appears to have been lost [13].…”

ChemInform Abstract: Synthetic Routes to Coelenterazine and Other Imidazo[1,2‐a]pyrazin‐3‐one Luciferins: Essential Tools for Bioluminescence‐Based Investigations

“…[109] Unfortunately,atoxicity by necrosis was observed in am ore recent report when injecting high doses of h-coelenterazine (149) into mice. [40j] Moreover,i ns erum,ahigher degree of autoxidation of this type of luciferin, which can be causedb ya lbumin [110] or IgG-binding domain, [111] was observedi nc omparison with buffers used for in vitro studies. [112] This problem is sometime compensated by as tronger bioluminescent signal.…”

Synthetic Routes to Coelenterazine and Other Imidazo[1,2‐a]pyrazin‐3‐one Luciferins: Essential Tools for Bioluminescence‐Based Investigations

“…Unfortunately, a toxicity by necrosis was observed in a more recent report when injecting high doses of h‐ coelenterazine ( 149 ) into mice 40j. Moreover, in serum, a higher degree of autoxidation of this type of luciferin, which can be caused by albumin110 or IgG‐binding domain,111 was observed in comparison with buffers used for in vitro studies 112. This problem is sometime compensated by a stronger bioluminescent signal.…”