Overexpression of Penicillin V Acylase from Streptomyces lavendulae and Elucidation of Its Catalytic Residues

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The pva gene from Streptomyces lavendulae ATCC 13664, encoding a novel penicillin V acylase (SlPVA), has been isolated and characterized. The gene encodes an inactive precursor protein containing a secretion signal peptide that is activated by two internal autoproteolytic cleavages that release a 25-amino-acid linker peptide and two large domains of 18.79 kDa (_-subunit) and 60.09 kDa (_-subunit). Based on sequence alignments and the three-dimensional model of SlPVA, the enzyme contains a hydrophobic pocket involved in catalytic activity, including Ser_1, His_23, Val_70, and Asn_272, which were confirmed by site-directed mutagenesis studies. The heterologous expression of pva in S. lividans led to the production of an extracellularly homogeneous heterodimeric enzyme at a 5-fold higher concentration (959 IU/liter) than in the original host and in a considerably shorter time. According to the catalytic properties of SlPVA, the enzyme must be classified as a new member of the Ntn-hydrolase superfamily, which belongs to a novel subfamily of acylases that recognize substrates with long hydrophobic acyl chains and have biotechnological applications in semisynthetic antifungal production.