I. Field of the Invention
This invention relates to a cloned tyrosine phenol-lyase gene, recombinant plasmids containing the tyrosine phenol-lyase gene, and to E. coli transformed with the recombinant plasmid, which are useful for the production of tyrosine phenol-lyase.
II. Description of the Related Art
Tyrosine phenol-lyase is a so called multifunctional enzyme, which catalyzes various reactions such as synthesis reactions of L-tyrosine and L-DOPA (Yamada, H. and Kumagai, H. (1975) Adv. Appl. Microbiol., vol. 19, pp. 249-288) and which is industrially important.
Various bacteria are known to produce tyrosine phenol-lyase. Among these, those belonging to genera Escherichia, Citrobacter, Aerobacter, Proteus and Erwinia which genera belong to Family Enterobacteriaceae have high tyrosine phenol-lyase activities (Yamada et al, supra).
Further, DNA fragments containing tyrosine phenol-lyase gene originating from Erwinia herbicola ATCC-21434 or Escherichia freundii AJ-2608 have been isolated and E. coli transformants containing these genes have tyrosine phenol-lyase activity (Japanese Laid Open Patent Application (Kokai) Nos. 259589/87 and 222682/88, respectively).
However, the tyrosine phenol-lyase activities of these microorganisms are low so that the microorganisms cannot be employed industrially. Further, when culturing these microorganisms, it is necessary to add to the culture medium tyrosine (Yamada et al, supra, or Japanese Laid Open Patent Application (Kokai) No. 259589/87) or isopropyl-.beta.-thiogalactoside (Japanese Laid Open Patent Application (Kokai) No. 222682/88). Further, if tyrosine is added to the culture medium in, for example, the production of DOPA, the product is likely to be contaminated with tyrosine On the other hand, isopropyl-.beta.-thiogalactoside is extremely expensive, so that it cannot be used in an industrial scale.