Comparison of arylsulphatases from Eimeria tenella (parasite) and chicken caecum (host)

Structural insights into choline-O-sulfatase reveal the molecular determinants for ligand binding

The first structures of a choline-O-sulfatase bound to different ligands are reported.

Choline-O-sulfatase (COSe; EC 3.1.6.6) is a member of the alkaline phosphatase (AP) superfamily, and its natural function is to hydrolyze choline-O-sulfate into choline and sulfate. Despite its natural function, the major interest in this enzyme resides in the landmark catalytic/substrate promiscuity of sulfatases, which has led to attention in the biotechnological field due to their potential in protein engineering. In this work, an in-depth structural analysis of wild-type Sinorhizobium (Ensifer) meliloti COSe (SmeCOSe) and its C54S active-site mutant is reported. The binding mode of this AP superfamily member to both products of the reaction (sulfate and choline) and to a substrate-like compound are shown for the first time. The structures further confirm the importance of the C-terminal extension of the enzyme in becoming part of the active site and participating in enzyme activity through dynamic intra-subunit and inter-subunit hydrogen bonds (Asn146^A–Asp500^B–Asn498^B). These residues act as the ‘gatekeeper’ responsible for the open/closed conformations of the enzyme, in addition to assisting in ligand binding through the rearrangement of Leu499 (with a movement of approximately 5 Å). Trp129 and His145 clamp the quaternary ammonium moiety of choline and also connect the catalytic cleft to the C-terminus of an adjacent protomer. The structural information reported here contrasts with the proposed role of conformational dynamics in promoting the enzymatic catalytic proficiency of an enzyme.

Three enzymes newly identified from the genus Eimeria and two more newly identified from E. maxima, leading to the discovery of some aliphatic acids with activity against coccidia of the domesticated fowl

Nine enzymes were detected in sporulated oocysts of Eimeria tenella and E. maxima, parasites of the domesticated fowl (Gallus gallus). Three enzymes, hydroxybutyrate dehydrogenase, alanine aminotransferase and gamma-glutamyltransferase, all identified for the first time in Eimeria of fowl, occurred both in E. tenella and in E. maxima. The remaining enzymes assayed had previously been found in various Eimeria species of fowl, although creatine kinase and glutamate dehydrogenase were hitherto unknown from E. maxima. The three enzymes newly recorded from Eimeria of fowl are of interest as potential genetic markers, and also as potential chemotherapeutic targets. The discovery of hydroxybutyrate dehydrogenase led to the demonstration of anticoccidial activity by some aliphatic acids. The paper also includes a list of the enzymes detected in Eimeria of fowl in previous studies.

Partial purification and characterization of acid phosphatase from sporulated oocysts of Eimeria tenella

Acid phosphatase of Eimeria tenella oocysts (Peak II) was purified 77-fold with a recovery of 26% using protamine sulfate precipitation, DEAE-cellulose chromatography and Sephadex G-200 gel filtration. This enzyme occurs in multiple forms as indicated by two peaks which can be separated by DEAE-cellulose chromatography and polyacrylamide gel electrophoresis. The partially purified enzyme has optimal activity at pH 4.5. With p-nitrophenyl phosphate the Km and Vmax values for (Peak II) were 25 mM and 1.57 mumol/min/mg protein, respectively. The enzyme (Peak II) is strongly inhibited by Hg++, Cu++, iodoacetamide, fluoride and molybdate. Tartrate and other divalent metal ions have no effect on enzyme activity. The partially purified Peak II phosphatase is not a glycoprotein as it is not absorbed on concanavalin-A Sepharose and its treatment with bacterial neuraminidase does not alter its elution profile through DEAE cellulose.