Functional characterization of X-prolyl aminopeptidase from Toxoplasma gondii.

In the present study, a recombinant aminopeptidase P (rTgAPP) from Toxoplasma gondii was expressed in Escherichia coli to evaluate its enzyme parameters. The rTgAPP showed strong activity against a synthetic substrate for aminopeptidase P at pH 8.0 with a K-m value of 0.255 mu M and a k(cat) value of 35.6 s(-1). The overall catalytic efficiency (k(cat)/K-m) of the rTgAPP was 139.6 x 10(5) M-1 s(-1). The activity of rTgAPP was enhanced by the addition of divalent cations and inhibited by bestatin. Deletion of TgAPP gene in the parasite through a CRISPR/Cas9 system resulted in inhibition of growth indicating the importance of TgAPP. Thus our findings reveal that TgAPP is an active enzyme in T. gondii and provide an insight into the function of TgAPP.