Efficient Nɛ-lauroyl-l-lysine production by recombinant ɛ-lysine acylase from Streptomyces mobaraensis

ɛ-Lysine acylase from Streptomyces mobaraensis (Sm-ELA), which specifically catalyzes hydrolysis of the ɛ-amide bond in various Nɛ-acyl-l-lysines, was cloned and sequenced. The Sm-ELA gene consists of a 1617-bp open reading frame that encodes a 538-amino acid protein with a molecular mass of 55,816 Da. An NCBI protein–protein BLAST search revealed that the enzyme belongs to the YtcJ-like metal-dependent amidohydrolase family, which is further characterized as the metallo-dependent hydrolase superfamily. The Sm-ELA gene was ligated into a pUC702 vector for expression in Streptomyces lividans TK24. Expression of recombinant Sm-ELA in S. lividans was approximately 300-fold higher than that in wild-type S. mobaraensis. The recombinant Sm-ELAs from the cell-free extract and culture supernatant were purified to homogeneity. The specific activities of the purified Sm-ELAs were 2500–2800 U/mg, which were similar to that obtained for the wild-type Sm-ELA. Using the cell-free extract of the recombinant S. lividans cells, Nɛ-lauroyl-l-lysine was synthesized from 500 mM l-lysine hydrochloride and 50, 100, or 250 mM lauric acid in an aqueous buffer solution at 37 °C. The yields were close to 100% after 6 and 9 h of reaction for 50 and 100 mM lauric acid, respectively, and 90% after 24 h for 250 mM lauric acid.