Involved in the biosynthesis of the parasiticide antibiotic grixazone. Catalyzes the oxidation of 3,4-aminohydroxybenzoate (3,4-AHBOA) to yield the corresponding quinone imine which is then non-enzymatically conjugated with the thiol group of N-acetylcysteine. The resultant compound is oxidized to its quinone imine enzymatically and is then dimerized non-enzymatically with another quinone imine oxidized by GriF to yield grixazone B. 3,4-aminohydroxybenzaldehyde (3,4-AHBAL) can also be used as substrate to yield grixazone A. In the grixazone biosynthetic pathway, it can also function as an o-aminophenol oxidase that catalyzes the formation of the phenoxazinone chromophore from alpha-aminophenol. It can also use 3,4-dihydroxybenzaldehyde, 2-amino-4-methylphenol and 3,4-dihydroxy-L-phenylalanine (L-DOPA) as substrates. In contrast to tyrosinases, it does not display monophenolase activity. 2 3-amino-4-hydroxybenzoate + H(+) + N-acetyl-L-cysteine + 2 O2 = CO2 + grixazone B + 4 H2O 4 2-aminophenol + 3 O2 = 2 2-aminophenoxazin-3-one + 6 H2O Binds 2 copper ions per subunit. Inhibited by 3-amino-4-hydroxybenzensulfonic acid, 4-hydroxy-3-nitrobenzaldehyde, L-tyrosine, P-hydroxybenzaldehyde. Activated by the copper chaperone GriE. kcat is 20 sec(-1) with alpha-aminophenol as substrate. kcat is 14 sec(-1) with 3,4-AHBAL as substrate. kcat is 18 sec(-1) with 2-amino-4-methylphenol as substrate. kcat is 0.8 sec(-1) with 3,4-dihydroxybenzaldehyde as substrate. kcat is 12 sec(-1) with catechol as substrate. kcat is 0.066 sec(-1) with L-DOPA as substrate. Optimum pH is between 8.5 and 10.5. Optimum temperature is 55 degrees Celsius. Cells lacking griE and griF show accumulation of the 3-amino-4-hydroxybenzaldehyde (3,4-AHBAL) intermediate. Belongs to the tyrosinase family.