Steven Keresztes-Nagy

Hybridization Experiments: Evidence of Dissociation Equilibrium in Hemerythrin

Partial succinylation of hemerythrin alters its electrophoretic mobility even though it remains an octameric macromolecule. Mixtures of this modified protein and unmodified hemerythrin generate species of intermediate electrophoretic mobility. Such behavior provides strong evidence that the octameric macromolecule is in mobile equilibrium with monomeric subunits.

Optical rotatory properties of hemerythrin in the ultraviolet range

Abstract Circular dichroic spectra have been recorded in the range from 200 to about 350 nm for methemerythrin, with its iron coordinated with different ligands. Major contributions to dichroic absorption in the 290-nm region can be ascribed to tyrosine residues, and there are also some contributions from the iron atoms. In the peptide n- π ∗ and π-π ∗ region, methemerythrin shows circular dichroic spectra similar to α-helical polypeptides. These spectra, and hence the presumed helix content (75%), do not change with changes in ligand bound to iron or upon dissociation of the protein into monomers.

Amino Acid Composition of Hemerythrin in Relation to Subunit Structure

Determination of the amino acid composition of coelomic hemerythrin from Golfingia gouldii shows 3 arginine residues and 10 to 11 lysine residues per protein subunit of 13,500 molecular weight. On this basis, the 28 to 30 major peptide spots revealed by electrophoresis and chromatography of tryptic hydrolysates would indicate two kinds of subunit. However, similar evidence from chymotryptic hydrolyses is not unequivocal, since the number of peptide spots is also compatible with an assumption of only one kind of chain. In addition to indicating the possible existence of two types of subunit, the peptide maps of enzymic digests of hemerythrin from individual animals shows at least one and perhaps more differences in peptide composition.

Studies on the Distribution of Cholinesterases: Activity in the Human and Dog Heart

Extract: The distribution and postnatal variation of cholinesterase (ChE) activity were studied in 25 human and 25 dog hearts. The observed distribution pattern is remarkably constant. In dog hearts, the pattern is as follows: sinus node (SN) > left atrium (LA) > right atrium (RA) > right ventricle (RV) ≃ left ventricle (LV). The average acetylcholinesterase (AcChE) activities as expressed in international units per g wet tissue are: 1.66 (SN), 1.14 (LA), 0.70 (RA), 0.22 (RV), and 0.21 (LV). In human hearts, the AcChE distribution follows the pattern of RA > LA > RV ≃ LV with corresponding average activities of 1.70, 1.38, 0.51, and 0.44 IU.The postnatal variation of ChE activity is most pronounced in the RA of the heart in both species. The average AcChE activity in the RA of the newborn puppies is 0.51 IU as compared with 2.27 IU in newborn infants. In the adult heart, however, the average atrial AcChE activity is nearly identical (1.02 IU) in both species.An additional difference is the large (34–64%) contribution of butyrylcholinesterase (BuChE) to the total activity in dog hearts whereas the contribution of BuChE is small (7–15%) in human hearts.Speculation: The relative AcChE activities and the distribution of this enzyme seem to follow the vagal innervation of the various parts of the heart. The low enzyme activities observed in the newborn puppies correlate well with histochemical and functional studies indicating incomplete development of the vagal innervation of the heart in this species at birth. In newborn babies, however, the vagal innervation of the heart is reportedly fully developed and the heart is markedly sensitive to vagal stimuli. The high AcChE activity present in the human heart at birth is compatible with these observations. Moreover, a decline of AcChE activity with age may represent a postnatal maturation process of the parasympathetic system of the heart which has not yet been appreciated.

Regional Distribution of Acetylcholinesterase in the Right Atria of Humans and Dogs

Summary: The regional distribution of acetylcholinesterase in the right atrium was determined by quantitative chemical measurements on hearts obtained from 14 infant and 9 adult humans at autopsy, and 9 adult dogs after termination of acute animal experiments. The atrium and interatrial septum were dissected, and the appendage was cut along its fold from the ventricular border to the superior vena cava. The atrium was cut into 20 consecutive sections. Homogenates (10% w/v) were prepared, centrifuged, and the supernatants were used for the enzyme assay by the method of Ellman. The acetylcholinesterase concentration [AChE] was mapped by section, or the sections were grouped into areas and mapped. The results show that: 1) in the dog, [AChE] is significantly higher in the nodal regions as compared to the appendicular areas, which contain the lowest [AChE]; 2) in the human, the [AChE] distribution pattern is qualitatively similar between the adult and infant, and in contrast to the dog, the appendicular areas contain the highest [AChE]; 3) for all areas studied, human infant [AChE] levels are significantly higher than human adult levels for corresponding areas. It is concluded that there is a distinct species difference between the regional distribution of the [AChE] in human and canine right atrium. Also, within humans, there is an age-related difference in the quantitative [AChE| levels. These species and age-related differences may reflect a varying pattern of distribution of the vagus nerve between the two species studied.Speculation: This study presents quantitative data about the regional distribution of AChE concentration within the right atria of adult dog, and adult and infant human hearts. Significant species and age-related differences were observed. Because a close correlation is known to exist between the concentration of acetylcholine, acetylcholinesterase, and choline acetylase in various regions of the peripheral and central nervous system, it is speculated that the differences in the distribution of acetylcholinesterase within the right atrium reported here reflect a difference in the pattern of cholinergic innervation between species.