Biotechnological production of L-tyrosine and derived compounds

The aromatic amino acid L-tyrosine is a compound with multiple applications ill the food, pharmaceutical, cosmetic and chemical industries. This review summarizes the current knowledge on the metabolic pathways involved in the synthesis of this amino acid and the strategies employed to develop and improve microbial production strains. Common strategies for L-tyrosine overproduction include the elimination of negative feedback control in key pathway enzymes and increasing the pool of the aromatic precursors phosphoenolpyruvate and erythrose-4-phosphate. Following these approaches, production strains have been generated that allow the synthesis of L-tyrosine with a yield from glucose corresponding to 80% of the theoretical maximum. Recent developments in the utilization of L-tyrosine as a substrate for microbial and enzymatic conversion into valuable products are also presented and discussed. For example, the production of the aromatic polymer melanin has been reported by the bioconversion of L-tyrosine using an Escherichia coli strain expressing a gene encoding the enzyme tyrosinase from Rhizobium etli. Metabolic engineering by expressing genes encoding the enzyme p-hydroxyphenylacetate 3-hydroxylase in an E. coli strain modified for L-tyrosine production from glucose results in the capacity to synthesize L-3,4-dihydroxyphenylalanine, a compound employed for treating Parkinson's disease. (c) 2012 Elsevier Ltd. All rights reserved.