# Characterization of luciferase from an Indian firefly Abscondita sp. (Coleoptera: Lampiridae)

## TL;DR

This paper characterizes a luciferase enzyme from an Indian firefly species, finding it lacks pH sensitivity unlike other fireflies.

## Contribution

The study reports the first enzymatic characterization of a luciferase from an Indian firefly species, revealing unique pH insensitivity.

## Key findings

- The luciferase from the Indian firefly has an optimum temperature of 30°C and pH of 7.0.
- Unlike other firefly luciferases, it does not show a red-shift in emission when pH is altered.
- RNA sequencing and E. coli expression were used to study the enzyme's properties.

## Abstract

Among the luminescent animals, fireflies have been extensively investigated throughout the world. Enzymatic characterization using recombinant proteins has been achieved after the first cloning of the Photinus pyralis luciferase gene. Firefly luciferase is pH sensitive, emitting a red‐shifted color when the pH of the reaction buffer is lowered. This trait is only known for fireflies and not in other luminescent beetles, including click beetles (Elateridae) and railroad worms (Phengodidae). Until now, firefly luciferases from North America, Central and South America, Europe, and East Asia have been intensively studied. Recently, molecular phylogenetic analyses using mitochondrial DNA have revealed relationships between firefly species in South Asia and India. However, the enzymatic characterization of luciferases from such species has not been thoroughly investigated. Here, we collected a firefly in India and enzymatically characterized its luciferase. Molecular phylogenetic analysis using cytochrome oxidase I suggested that this firefly is closely related to the genus Abscondita. The luciferase gene obtained from the RNA sequencing (RNA‐Seq) was expressed using Escherichia coli and was used to characterize the luciferase. Its optimum temperature and pH were 30°C and 7.0, respectively. The maximum emission wavelength was around 570 nm when a pH 6.0 or 8.0 reaction buffer was used, and no apparent red shift was observed.

(Left panel) Abscondita sp. (Lampyridae) collected in Guwahati, India. Scale bar = 5 mm. ( Right panel) Spectrum analysis of recombinant luciferase derived from this species at different pH. Unlike the other Lampyridae luciferases, this one showed pH insensitivity.