In the cuticle, catalyzes the hydrolysis of beta-alanyl-dopamine releasing dopamine and beta-alanine; dopamine is a metabolite involved in the pigmentation and sclerotization of the insect cuticle (PubMed:16299587, PubMed:20439462, PubMed:21571070, PubMed:8580497). In the photoreceptor cells, catalyzes the hydrolysis of carcinine releasing histamine and beta-alanine contributing to the recycling of the neurotransmitter histamine in the optical nerve system (PubMed:12486147, PubMed:16299587, PubMed:20439462, PubMed:5782111). Also, regulates the cuticular hydrocarbon composition in females (PubMed:31118901).

(UniProt, Q9W369)

Body color varies from light tan to almost wildtype. Easiest to identify by light tan antennae; male easier than female. Larval mouthparts in mutant alleles, t1, t2, and t3 lighter than normal at basal prongs; classifiable with difficulty in larvae (Brehme, 1941, Proc. Nat. Acad. Sci. USA 27: 254-61). Neurological defect first observed in t1 by McEwen (1918), who reported that the mutant flies behaved as if they were nonphotactic in his test apparatus (tube with light at one end); Benzer (1967) and Pak et al., (1969), using a similar but more elaborate apparatus and EMS-induced tan alleles, reached the same conclusion. In a Y-maze test for phototaxis, however, tan mutants are sensitive to light (Hadler, 1984, Biol. Bull. 126: 264-73). In the electroretinogram (ERG) tracing obtained when one electrode is inserted in the first optic ganglion (lamina) below the ommatidia, the on- and off-transients of tan flies are reduced or missing, but the other ERG components are present, indicating that the mutant is not blind although it appears behaviorly blind in some tests. Mosaic studies (Hotta and Benzer, 1970, Proc. Nat. Acad. Sci. USA 67: 1156-63) indicate that the ERG phenotype of tan is cell autonomous. The optomotor responses of mutants to horizontal and vertical movements are abnormal in that light intensity thresholds for responses are raised, the extent depending on the allele (Heisenberg, 1971, DIS 46: 68; Heisenberg and Gotz, 1975; Heisenberg and Buchner, 1977). No walking optomotor responses are detected, but there can be positive responses in flying optomotor tests if the rotating vertical stripes are relatively wide. The enzyme tyrosinase, which converts tyrosine to 3,4-dihydroxyphenylalanine (DOPA), is formed in tan adults (Horowitz). Dopamine, an important component of catecholamine metabolism (involved in both melanization of cuticle and synthesis of neurotransmitters), has been found in reduced amounts (about 60% of the wild-type concentration) in t1 and t5 (Konopka, 1972). The dopamine was detected only in late pupae that show some pigmentation and in adult flies. One of the enzymes involved in the formation of dopamine, β-alanyldopamine hydrolase (BAH), shows no activity in t/t and t/Y mutants and reduced activity in t/+ heterozygotes as compared to wild-type (Black, Pentz, and Wright). This dosage effect implicates tan as the structural gene for BAH (Wright, 1987). The mutant tan is defective in courtship behaviors, the males showing aberrant visually-mediated responses to moving female flies (Cook, 1980, Biol. Cybernet. 37: 41-51; Tompkins, Gross, Hall, Gailey, and Siegel, 1982, Behav. Genet. 12: 295-307).