TYR Gene

The TYR gene (TYR stands for "tyrosinase") is a protein-coding gene located on chromosome 11q14.3. The enzyme encoded by the TYR gene catalyzes the first two steps and at least one additional step in the conversion of tyrosine to melanin. The copper-containing enzyme has both tyrosine hydroxylase and dopa oxidase catalytic activity and requires copper for its function.

Thus, the encoded enzyme catalyzes the first and rate-limiting step in the reaction cascade leading to melanin production from tyrosine. Furthermore, in addition to the hydroxylation of tyrosine to DOPA (3,4-dihydroxyphenylalanine), it also catalyzes the oxidation of DOPA to DOPA-quinone and possibly the oxidation of DHI (5,6-dihydroxyindole) to indole-5,6-quinone.

Mutations in the tyrosinase (TYR) gene lead to the different variants of oculocutaneous albinism type I (OCA type IA/IB/ITs).

Non-pathological polymorphisms lead to different skin pigmentation.

OCA1, caused by mutations in the TYR gene, is clinically divided into three variants: type IA, OCA1A (classic form), characterized by the complete absence of tyrosinase activity due to the production of an inactive enzyme, type IB (OCA1B; 606952), characterized by decreased tyrosinase activity (Liu N et al. 2014), and typeI TS the temperature-sensitive oculocutaneous albinism.

OCA2 (203200), OCA3 (203290), and OCA4 (606574) are somewhat milder forms of the disorder caused by mutations in the OCA2 (611409), TYRP1 (115501), and MATP (SLC45A2; 606202) genes, respectively.

OCA5 (615312) was mapped to chromosome 4q24.

OCA6 (see 113750) is caused by a mutation in the SLC24A5 gene (609802).

OCA7 (615179) is caused by a mutation in the C10ORF11 gene (614537).

OCA8 (619165) is caused by a mutation in the DCT gene (191275).

1. Feng H et al. (2015) TYR as a multifunctional reporter gene regulated by the Tet-on system for multimodality imaging: an in vitro study. Sci Rep 5:15502.
2. Liu N et al (2014) Tyrosinase gene mutations in the Chinese Han population with OCA1. Genet Res (Camb) 96:e14.