Prolidase is a Mn(2+)-dependent
dipeptidase that cleaves imidodipeptides containing C-terminal
proline or
hydroxyproline. In humans, a lack of
prolidase activity causes
prolidase deficiency, a rare autosomal recessive disease, characterized by a wide range of clinical outcomes, including severe skin lesions,
mental retardation, and
infections of the respiratory tract. In this study, recombinant
prolidase was produced as a fusion
protein with an N-terminal
histidine tag in eukaryotic and prokaryotic hosts and purified in a single step using immobilized
metal affinity chromatography. The
enzyme was characterized in terms of activity against different substrates, in the presence of various bivalent
ions, in the presence of the strong inhibitor
Cbz-Pro, and at different temperatures and pHs. The recombinant
enzyme with and without a tag showed properties mainly indistinguishable from those of the native
prolidase from fibroblast lysate. The
protein yield was higher from the prokaryotic source, and a detailed long-term stability study of this
enzyme at 37 degrees C was therefore undertaken. For this analysis, an 'on-column' digestion of the N-terminal His tag by
Factor Xa was performed. A positive effect of Mn(2+) and GSH in the incubation mixture and high stability of the untagged
enzyme are reported. Poly(
ethylene glycol) and
glycerol had a stabilizing effect, the latter being the more effective. In addition, no significant degradation was detected after up to 6 days of incubation with cellular lysate. Generation of the
prolidase in Escherichia coli, because of its high yield, stability, and similarity to native
prolidase, appears to be the best approach for future structural studies and
enzyme replacement therapy.