In its first step, the enzyme converts tyrosine amino acid into dihydroxy phenylalanine (DOPA) and then to DOPAquinone.1 Phenotypically, the TYR gene defect is categorized into OCA1A
Clinically it is sub-categorized into OCA1A characterized by complete loss of tyrosinase activity and OCA1B characterized by reduced enzyme activity4.
Iris color in these patients is same as like in OCA1A cases.
The most severe phenotype, OCA1A
or tyrosinase-negative albinism, results from a complete lack of enzyme activity and pigment remains completely absent in the skin, hair and eyes throughout life.
Purohit, "Mutational analysis of TYR gene and its structural consequences in OCA1A
," Gene, vol.
OCA 1'de tirozinaz ekspiesyonunda degiskenlik ve melanin pigmenti sentezindeki bir seri defekt sonucu tirozinden dihidroksifenilalanin sentezi bozulur Defektif tirozinaz enzimi uretimi nedeniyle enzim aktivitesinin hic olmadigi OCA1A
ve enzim aktivitesinin mevcut fakat dusuk seviyede bulundugu OCA1B alt tiplerine ayrilir.