链霉菌酪氨酸酶基因的克隆与表达

本文综述了近年来对链霉菌酪氨酸酶基因的研究。由酪氨酸酶合成黑色素是链霉菌属各个种的共同特性，并受到酪氨酸酶基因的控制。链霉菌几个种的酪氨酸酶基因已克隆到，其产黑色素的特性使之作为重要的标记基因得以广泛应用，同时，该基因在链霉菌的不同种及不同属的微生物中得到了高水平的表达。链霉菌酪氨酸酶基因表达调控的分子机制也得到较深入的研究。

Cloning and Expression of the Tyrosinase Gene from Streptomyces

Tyrosinase(EC 1.14.18.1),which appears to be widely distributed in plant and animal kingdoms,bacteria and fungi,is the key enzyme in the pathway of melanin synthesis.Melanin-producing catalyzed by the tyrosinase is the universal characteristic of Streptomyces species.Streptomyces plasmid PIJ702 is a useful and convenient cloning vector in the study of genetic analysis of Streptomyces because it carries the easily identified tyrosinase gene for melanin production as a selectable marker.On the basis of the Plasmid PIJ702,a cloning vector(pMT603) for studying plasmid stability,functions and a promoter-probe vector(pMX100) employing the tyrosinase encoding gene as a reporter have been constructed.PIJ702 is a high copy number plasmid.Its transformant of Streptomyces species had greatly higher level of tyrosinase activity.Furthermore,tyrosinase gene from Streptomyces have been cloned and functionally expressed in E.coli and in Streptororcus thermophilus.The tyrosinase operon(melC) is composed of two genes that encode MelC1 and MelC2 protein.MelC1 has been suggested as a trans-activator which can facilitate the incorporation of copper into the apotyrosiase (MelC2).