RESUMO
The gene for tyrosinase has been mapped to the long arm of chromosome 11 at 11q14-21. The gene is at least 50Kb in length and its coding region is divided into five exons. Until now several mutations of the tyrosinase gene have been identifed in patient with typical oculocutaneous albinism (OCA) who are responsible for tyrosinase negative OCA. It may be possible to determine the types of OCA by measuring the hairbulb tyrosinase activity. Hairbulb tyrosinase activity was examined in a Korean albino to determine the type of OCA. And also tyrosinase assay was carried out in normally pigmented individuals and all members of a Korean albino's family to examine the tyrosinase activities. Five exons of tyrosinase gene from a Korean albino were amplified by polymerase chain reaction. Each amplified exon segments were independently subcloned and DNA sequences of clones were determined. The results obtained were as follows : 1. A Korean albino had no measurable hairbulb tyrosinase activity and was identified as type IA (tyrosinase negative) oculocutaneous albinism. 2. Normally pigmented individuals had different ranges of hairbulb tyrosinase activity. 3. A Korean albino had two single base insertions within exon V (between 337bp and 338bp, 353bp and 354bp) of tyrosinase gene. These insertional mutations might disrupt tyrosinase function and were associated with a total lack of melanin biosynthesis.