The pva gene from Streptomyces lavendulae ATCC 13664, encoding a novel penicillin V acylase ( Sl PVA), 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 (α-subunit) and 60.09 kDa (β-subunit). Based on sequence alignments and the three-dimensional model of Sl PVA, the enzyme contains a hydrophobic pocket involved in catalytic activity, including Serβ1, Hisβ23, Valβ70, and Asnβ272, 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 Sl PVA, 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.
展开▼
