Catalyzes the oxidation of a wide variety of organic substrates, including bilirubin, syringaldazine (SGZ), 2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS) and dimethoxyphenol (DMP). No oxidation of Fe(2+) or guaiacol. 4 hydroquinone + O2 = 4 benzosemiquinone + 2 H2O Binds 4 copper ions per subunit. Inhibited by 1 mM NaN(3), 10 mM thiourea, 10 mM 1,10-phenanthroline, 0.1 mM DL-dithiothreitol (DTT) and 1 mM L-cysteine. The inhibition by DTT and L-cysteine is likely caused by reduction of the oxidized substrate and not by inhibition of the enzyme. kcat is 9.9 sec(-1) with 2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid as substrate. kcat is 21.7 sec(-1) with syringaldazine as substrate. Optimal activity at 200 mM salt, with 65% activity at 1 M NaCl. Optimum pH is 6.0 for the oxidation of 2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid and 8.4 for the oxidation of syringaldazine. Optimum temperature is 45-50 degrees Celsius. Highly thermostable. Exported by the Tat system. Glycosylated. Belongs to the multicopper oxidase family.