Avian pancreatic polypeptide fragments refold to native aPP conformation when combined in solution: A CD and VCD study

An equimolar mixture of avian pancreatic polypeptide (aPP) fragments aPP(1-11)-NH2 and Ac-aPP(12-36) had an electronic circular dichroism (ECD) spectrum that was similar to that of whole aPP in H2O and even more so in 30% (v/v) trifluoroethanol (TFE) in 15 mM Na2HPO4, but was different from the sum of the spectra of the individual fragments. The vibrational circular dichroism (VCD) spectrum of the combined fragments in 30% (v/v) TFE in 15 mM Na2HPO4 in D2O was also similar to that of the intact aPP and unlike the sum of the VCD spectra of the fragments. The interaction of these fragments is thus sufficient to support the conformation of whole aPP. This study demonstrates that VCD, in combination with ECD, is useful for the study of protein-protein interactions.

A role for pancreatic polypeptide in the regulation of gastric emptying and short-term metabolic control

CONTEXT

Previous studies using pancreatic polypeptide (PP) infusions in humans have failed to show an effect on gastric emptying, glucose metabolism, and insulin secretion. This might be due to the use of nonhuman sequences of the peptide.

OBJECTIVE

The objective of this study was to use synthetic human PP to study gastric emptying rates of a solid meal and postprandial hormone secretion and glucose disposal as well as the gastric emptying rate of water.

DESIGN

This was a single-blind study.

SETTING

The study was performed at a university hospital.

PARTICIPANTS

Fourteen healthy adult subjects were studied.

INTERVENTIONS

Infusion of saline or PP at 0.75 or 2.25 pmol/kg.min was given to eight subjects (gastric emptying of solid food), and infusion of saline or PP at 2.25 pmol/kg.min was given to six subjects (gastric emptying of water).

MAIN OUTCOME MEASURES

The main outcome measures were gastric emptying of solids (scintigraphy), hunger ratings (visual analog scale), and plasma concentrations of PP, insulin, glucagon, somatostatin, glucagon-like peptide 1, glucose, and gastric emptying of plain water (scintigraphy).

RESULTS

PP prolonged the lag phase and the half-time of emptying of the solid meal. The change in hunger rating, satiety, desire to eat after the meal, or prospective consumption was not affected. The postprandial rise in plasma glucose was prolonged by PP. The postprandial rise in insulin was also delayed by PP. PP had no significant effect on the emptying of water.

CONCLUSIONS

PP inhibits gastric emptying of solid food and delays the postprandial rise in plasma glucose and insulin. PP is suggested to have a physiological role in the pancreatic postprandial counterregulation of gastric emptying and insulin secretion.

Primary B-cell response to neuropeptide Y and bovine pancreatic polypeptide

An analysis of the murine primary response to protein epitopes has been made with two small highly structured proteins, neuropeptide Y (NPY) and bovine pancreatic polypeptide (BPP), both of 36-amino acid residue length and containing helical structures. A group of cell lines producing monoclonal IgM antibody have been prepared consisting of six anti-NPY and two anti-BPP. The VH nucleotide sequences have been determined and characterized as germ-line either by identity to established germ-line sequences or by inference from the germ-line character of the D and JH segments. The intrinsic association constants for the homologous ligands have been estimated to range from 10(4) to 10(7) M-1 based on competitive ELISA. No severe restriction in the utilization of VH families, D segments or JH segments appears to be involved in this response. Among the eight cell lines, three VH families were represented as well as all three families of D segments and all of the JH segments, although some preference for JH3 was indicated. The length of the N(D)N sequences was also not subject to restriction, ranging from 9 to 29. Two unusual features of the CRD3s were noted, one involving the utilization of an uncommon DSP2 segment and the other the apparent occurrence of a D-D fusion.

Solid-phase synthesis of human pancreatic polypeptide

The 36-residue sequence of human pancreatic polypeptide (HPP) was synthesized by solid-phase methodology, cleaved from the benzhydrylamine resin by HF treatment, and purified by gel filtration, ion exchange, and partition chromatography. In addition to the usual criteria, the homogeneity of the final product was examined by reversed phase high performance liquid chromatography. This technique was also used to isolate and characterize the cyanogen bromide cleavage fragments, and finally to compare the synthetic product with native human, bovine, and porcine pancreatic polypeptide isolated from natural sources. The purified HPP, like native PP, was a potent inhibitor of pancreatic secretion in the dog.