Discovery of Novel Tyrosine Ammonia Lyases for the Enzymatic Synthesis of p-Coumaric Acid

p-Coumaric acid (p-CA) is a key precursor for the biosynthesis of flavonoids. Tyrosine ammonia lyases (TALs) specifically catalyze the synthesis of p-CA from l-tyrosine, which is a convenient enzymatic pathway. To explore novel and highly active TALs, a phylogenetic tree-building approach was conducted including 875 putative TALs and 46 putative phenylalanine/tyrosine ammonia lyases (PTALs). Among them, 5 TALs and 3 PTALs were successfully characterized and found to exhibit the proposed enzymatic activity. The TAL from Chryseobacterium luteum sp. nov (TAL(clu)) has the highest affinity (K-m=0.019 mm) and conversion efficiency (k(cat)/K(m=)1631 s(-1) . mm(-1)) towards l-tyrosine. The reaction conditions for two purified enzymes and their E. coli recombinant cells were optimized and p-CA yields of 2.03 g/L after 8 hours by TAL(clu) and 2.35 g/L after 24 h by TAL from Rivularia sp. PCC 7116 (TAL(rpc)) in whole cells were achieved. These TALs are thus candidates for the construction of whole-cell systems to produce the flavonoid precursor p-CA.

Automated summary

p-Coumaric acid (p-CA) is a key precursor for flavonoid biosynthesis, and tyrosine ammonia lyases (TALs) catalyze the synthesis of p-CA from l-tyrosine. In this study, 875 putative TALs and 46 putative phenylalanine/tyrosine ammonia lyases (PTALs) were analyzed, and 5 TALs and 3 PTALs were characterized and found to exhibit the proposed enzymatic activity. The TAL from Chryseobacterium luteum sp. nov (TAL(clu)) showed the highest affinity and conversion efficiency towards l-tyrosine. Optimization of reaction conditions resulted in p-CA yields of 2.03 g/L after 8 hours by TAL(clu) and 2.35 g/L after 24 hours by TAL from Rivularia sp. PCC 7116 (TAL(rpc)). These TALs are potential candidates for the production of flavonoid precursor p-CA using whole-cell systems.