We report here on the purification, characterization, molecular cloning, and expression of a new aminoacylase, initially isolated from the supernatant of
Streptomyces mobaraensis (
Sm-AA). Purified wild-type
Sm-AA was found to be a monomeric protein with a molecular mass of 55 kDa. The cloned gene of
Sm-AA contained an ORF of 1,383 bp, encoding a polypeptide of 460 amino acids. A BLAST search revealed that
Sm-AA belongs to the peptidase M20 family, with identities to a hypothetical protein from
Streptomyces pristinaespiralis, a putative peptidase from
Streptomyces avermitilis, peptidase M20 from
Frankia sp., succinyl-diaminopimelate desuccinylase from
Hemophilus influenzae, and aminoacylase-1 from porcine kidney at 89, 88, 67, 29, and 25% respectively. The
Sm-AA gene was subcloned into an expression vector, pSH19, and was expressed in
Streptomyces lividans TK24. The amount of the recombinant
Sm-AA expressed in the
S. lividans cells was approximately 42-fold higher than that of
Sm-AA found in the supernatant of
S. mobaraensis.
Sm-AA showed high hydrolytic activity towards various
N-acetyl-
L-amino acids and
N-(middle/long)-chain-fatty-acyl-
L-amino acids, with a preference for the acyl derivatives of
L-Met,
L-Ala,
L-Cys,
etc. with an optimum pH and temperature for reaction of about 7.5 and 50 °C (at pH 7.5).
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