Effect of the disruption of body fluid balance on pyroglutamyl aminopeptidase (Type-1) in rat brain structures

Visual identification of gut bacteria and determination of natural inhibitors using a fluorescent probe selective for PGP-1

PGP-1 is a bacterial hydrolase that can hydrolyze the amide bond of the l-pyroglutamate (L-pGlu) residue at the amino terminus of proteins and peptides. Guided by the biological function of PGP-1, an off-on NIR fluorescent probe DDPA was developed for the visual sensing of PGP-1 by conjugating pyroglutamic acid (recognition group) and DDAN (fluorophore). Using intestinal bacteria cultivation, eight bacteria strains with active PGP-1 were identified and cultivated efficiently using DDPA. In addition, three natural inhibitors against PGP-1 were isolated from the medical herb Psoralea corylifolia, which could be used to interfere with bacterial metabolism in the gut. As such, the fluorescent probe DDPA provides an efficient method and potential tool for the investigation of intestinal microbiota.

Cloning and heterologous expression of bovine pyroglutamyl peptidase type-1 in Escherichia coli: purification, biochemical and kinetic characterisation

We describe the cloning, expression and purification of the bovine XM866409 form of pyroglutamyl peptidase type-1 (PAP1). The cloned nucleotide sequence has an ORF coding for a primary sequence of 209 amino acid residues, which displays 98% identity with the human AJ278828 form of the enzyme. Three amino acid residues at positions 81, 205 and 208 were found to vary between the two sequences. The recombinant bovine PAP1 with a C-terminal His(6) tag (rBtaPAP1(6H)) was expressed in Escherichia coli XL10-Gold cells and purified by immobilised nickel ion affinity chromatography resulting in a yield of 2.6 mg of PAP1 per litre of culture. Purified rBtaPAP1(6H) had a specific activity of 3633 units mg(-1). SDS-PAGE revealed a band for bovine PAP1 with a molecular weight of approximately 24 kDa, which is in good agreement with previously reported data on PAP1. The K (m) and k (cat) values obtained for rBtaPAP1(6H) were 59 muM and 3.5 s(-1), respectively. The optimum pH for activity was 9.0-9.5 and the optimum temperature was 37 degrees C. rBtaPAP1(6H) was found to have an absolute requirement for the thiol-reducing agent DTT, consistent with the expected property of a cysteine protease. Kinetic studies using the peptides pGlu-His-Pro-NH(2) (TRH), pGlu-Ala and pGlu-Val revealed K (i) values of 44.1, 141 and 652.17 microM, respectively. The lowest K (i), observed for Thyrotropin-releasing Hormone (TRH), indicates that rBtaPAP1(6H) has a higher affinity for tripeptides over dipeptides.

Distribution of peptidase activity in teleost and rat tissues

Peptides play important roles in cell regulation and signaling in many tissues. The actions of peptides are regulated by peptidases. Although the activity of these enzymes has been thoroughly characterized in mammals, little is known about their presence or function in fish. In the present study, we compared the activity of several peptidases in selected tissues (pituitary gland, different brain areas, kidney and gills) of the gilthead sea bream and rainbow trout with that found in similar rat tissues (lungs studied in place of gills). Soluble puromycin-sensitive aminopeptidase showed the highest values in the pituitary gland of the sea bream, whereas the membrane-bound form was found to be more active in the trout kidney. Very high levels of activity of aminopeptidase N were detected in trout and sea bream plasma. In contrast, the highest levels of activity of aminopeptidase B were found in rat tissues, with the exception of the gills of the trout. Aminopeptidase N levels tended to be higher in sea bream tissues with respect to those of trout. In contrast, the level of activity of aminopeptidase B was found to be consistently much higher in trout tissues than in those of the sea bream. Prolyl endopeptidase activity was principally detected in the pituitary gland and in the brain areas of teleosts. These differences between species could be related to different mechanisms of osmoregulation in saltwater- and in freshwater-adapted fish.

Cystyl aminopeptidase activity in the plasma, viscera and brain of the snake Bothrops jararaca

The relationship between plasma osmolality and cystyl aminopeptidase was characterized in the snake Bothrops jararaca and comparisons were made with the emerging picture of this relationship in rats. The profile of cystyl aminopeptidase activity under basal conditions was determined in the soluble and membrane-bound forms in visceral organs and in the central nervous system in comparison with that of alanyl aminopeptidase. The regional localization of cystyl and alanyl aminopeptidase activities was studied in the central nervous system. The basal level of plasma cystyl aminopeptidase, four- to six-fold higher than in rats, suggests its importance to help regulate circulating levels of neurohypophysial peptides in B. jararaca snake. The osmotic sensitivity of this plasma enzyme, undetectable in male, but about three-fold higher in female snakes than in rats, reveals a sexual dimorphism. In marked contrast to those observed in rats, low levels of soluble and particulate forms in the kidney indicate that cystyl aminopeptidase plays a minor metabolizing role at this anatomical location in B. jararaca. Despite of the regional-specific divergence between the levels of rat and snake enzymes, the bilaterally symmetric pattern of the diencephalic distribution of alanyl aminopeptidase reflects functional homologies between these two distantly related species.