molecules of 35 kDa components, making it a heterotetrameric molecule. The proteins signal the enzyme for secretion in luminescence, catalyzed by the protein 19 kDa [3,4,7]. The luciferase has many cysteine residues that stabilize the enzyme in extracellular environments using disulfide bonds [5]. 19 kDa Protein This catalytic component of OpLuc has 196 amino acids [3] with one cysteine in the carboxyl terminus and is distinct from proteins found in other luciferases [4]. The protein is made up of two domains with repetitive sequencing of Ia-c and Ila-d in the peptide chain [4]. It is thought to be the protein to cause the bioluminescent reaction of O.gracilirostris, but functions ineffectively without its larger, subunit counterpart [3,4]. Although the crystal structure of OpLec has yet to be completely analyzed and mapped, 19 kDa experimentally expressed in mammalian cells (regarded as KAZ [7]). The protein was isolated and mutated to catalyze a bright and sustained luminescent reaction to create an engineered luciferase, NanoLuc (NLuc), and a coelenterazine analogue (furimazine) to be used as a cellular reporter [5,8]. A mutated ribbon model of the 19 kDa protein (named nanoKaz) is shown in figure 2. 35 kDa Protein The lesser known component of the OpLuc enzyme has 320 amino acids [3] with 11 cysteine and 5 leucine molecules [4]. The amino terminus of the protein was experimentally concluded to begin at 39 amino acids [3]. It is thought to stabilize 19 kDa and is not thought to be affect by substrate specificity [3], however its exact function is not known [3,4,7]. Mechanism Although originally thought to have the exact same mechanism as the Renilla luciferase [1], this luminescence has two possible reaction routes [2], as shown in figure 3. In the top route, Oplophorus luciferin (the coelenterazine displayed as I in the scheme) is oxidized when it combines with O2(radioactively labelled O18 was used in lab experiment) in a water medium and uses a dioxetane peroxide intermediate resulting in a product and coelenteramide (II in the scheme). The lower pathway does not use an intermediate and has rapid exchanges of oxygen with the water medium. Studies show there is less product yield and is suggested to have partial involvement in the overall reaction [2]. It should be noted, however, it is likely contamination during experiments demonstrated higher yield than was occurring for the lower pathway, making this pathway highly unlikely in natural conditions [2].