Tyrosine ammonia lyase catalyzes the deamination of l-tyrosine to trans-coumaric acid. A novel tyrosine ammonia lyase-encoding gene, bagA, was cloned and sequenced from bagremycins-producing strain Streptomyces sp. Tu 4128 whose protein product contains a Ala-Ser-Gly segment in the active site. The disruption of the bagA gene abolished trans-coumaric acid and bagremycins production. trans-coumaric acid restored the formation of bagremycin A in the mutant, but not bagremycin B. Thus, trans-coumaric acid is a precursor for biosynthesis of bagremycins and the bagA gene codes for tyrosine ammonia lyase to synthesize trans-coumaric acid. This is a novel bacterial tal gene reported in actinomycetes for the second time and for the first time in a Streptomyces sp.