Multicopper oxidase that catalyzes the oxidation of a variety of substrates, including phenolic and non-phenolic compounds. Substrates include syringaldazine (SGZ), 2,6-dimethoxyphenol (2,6-DMP) and the non-phenolic compound 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) (PubMed:11514528, PubMed:11884407, PubMed:18307408, PubMed:20200715, PubMed:22481612, PubMed:27050268). Has no tyrosinase activity (PubMed:11514528). Is implicated in the biosynthesis of a brownish pigment that characterizes sporulating colonies of B.subtilis, and which appears to be a melanin-like product and to confer protection against UV light (PubMed:2821284, PubMed:11514528, PubMed:11884407). In vitro, also shows strong bilirubin oxidase (BOD) activity, and can catalyze the oxidation of free bilirubin (UB), direct bilirubin (conjugated with glucuronic acid, DB) and ditaurobilirubin. 4 hydroquinone + O2 = 4 benzosemiquinone + 2 H2O 2 bilirubin IXalpha + O2 = 2 biliverdin IXalpha + 2 H2O Binds 4 copper ions per subunit. The 4 copper centers adopt structures classified as type 1, type 2 and type 3. Inhibited by azide. kcat is 16.8 sec(-1) with ABTS as substrate (PubMed:11884407). kcat is 322 sec(-1) with ABTS as substrate (PubMed:18307408). kcat is 144 sec(-1) with ABTS as substrate (PubMed:22481612). kcat is 3.7 sec(-1) with SGZ as substrate (PubMed:11884407). kcat is 80 sec(-1) with SGZ as substrate (PubMed:18307408). kcat is 36 sec(-1) with 2,6-DMP as substrate (PubMed:18307408). kcat is 33 sec(-1) with 2,6-DMP as substrate (PubMed:22481612). kcat is 1.59 sec(-1) with free bilirubin as substrate (PubMed:33618226). kcat is 4.77 sec(-1) with direct bilirubin as substrate (PubMed:33618226). kcat is 140 sec(-1) for O(2) consumption (PubMed:22481612). Optimum pH is 7 for SGZ and bilirubin oxidation (PubMed:11514528, PubMed:11884407, PubMed:16391148). Optimum pH is about 4 for ditaurobilirubin oxidation (PubMed:16391148). Optimum pH is below 3.0 for ABTS oxidation (PubMed:11884407). Optimum pH is 8.0 for UB oxidation, whereas optimum pH for DB oxidation is 5.5 (PubMed:33618226). Highly thermostable (PubMed:11884407, PubMed:16391148). Optimum temperature is 45 degrees Celsius for SGZ oxidation (PubMed:11514528). Optimum temperature is 75 degrees Celsius with ABTS as substrate (PubMed:11884407). Monomer. Localized to the surface layers of the endospore. Expression is switched on about four to five hours after the onset of sporulation, a time that corresponds approximately to the stage of spore coat synthesis and deposition. Glu-498, located within the entrance channel of the trinuclear center, plays a key role in the protonation events that occur at the trinuclear center and in its stabilization, controlling therefore the binding of dioxygen and its further reduction (PubMed:20822511, PubMed:20200715). Asp-116, situated in the exit channel of the trinuclear center, and its hydrogen bond connectivity are highly relevant for the overall reactivity of the laccase but do not appear to play a critical structural role (PubMed:22481612). Disruption of the gene does not prevent spore formation, but mutant is blocked in the appearance of the brown pigment characteristic of colonies of wild-type sporulating cells. When expressed on the surface of E.coli cells, CotA was shown to possess improved enzymatic properties, including higher thermal stability and stronger inhibitor tolerance. It has high enzymatic activity against three industrial dye types: an anthraquinone dye, Acid Blue 62, a triphenylmethane dye, Malachite Green, and an azo dye, Methyl Orange. It may help decrease the costs and simplify wastewater treatment, and therefore, surface-displayed CotA shows a great potential for industrial-scale dye decolorization. CotA is also a promising candidate for the clinical determination of direct bilirubin and total bilirubin, which are significant diagnostic marker of liver function and cancer. Belongs to the multicopper oxidase family.