Roderich Walter

Leucylglycinamide Released from Oxytocin by Human Uterine Enzyme

Uteri of pregnant and nonpregnant women contain enzymic activities which inactivate oxytocin. A potent enzyme, which has been partially purified from uterine homogenates, cleaves the prolyl-leucyl peptide bond of oxytocin. This findinig associates for the first time the release of the dipeptide leucylglycinamide with the degradation of neurohypophyseal hormones.

Production of MSH-release-inhibiting hormone by a particulate preparation of hypothalami: mechanisms of oxytocin inactivation.

Abstract Hypothalami of rabbit and rat contain a membrane-bound exopeptidase which stepwise degrades radioactively-labeled oxytoxin ([9-glycinamide-1- 14 C]-oxytocin) to give labeled H-Pro-Leu-Gly-NH 2 , which is the release-inhibiting hormone of MSH (MSH-R-IF). Supernatant fractions of rabbit and rat hypothalami contain predominantly an endopeptidase which releases H-Leu-Gly-NH 2 from oxytocin.

Complete amino acid sequence of bovine neurophysin II

Abstract The complete amino acid sequence of bovine neurophysin II, a 97 amino acid protein which specifically binds the posterior pituitary hormones oxytocin and arginine vasopressin, is proposed.

Chromatographic separation of isologous sulfur- and selenium-containing amino acids: Reductive scission of the selenium-selenium bond by mercaptans and selenols

Abstract Racemic Se-methylselenocysteine, selenocystine, selenomethionine, selenoethionine, and Se-benzylselenocysteine are separated from their corresponding sulfur isologs by ion-exchange chromatography. The reason was uncovered for previous failures to obtain reproducible color values for selenocystine. The selenium-selenium bond of selenocystine is cleaved by mercaptans and selenols, yielding acyclic molecules with selenium-sulfur or selenium-selenium bonds. The diselenide-sulfhydryl and diselenide-selenol interchange reactions, which occur over a wide pH range, must be taken into account during analytical investigations involving mixtures of diselenides, and/or thiols, and/or selenols. Treatment of peptides containing selenocystine or selenocysteine residues (1-selenooxytocin, 6-selenooxytocin, deamino-1-selenooxytocin, deamino-6-selenooxytocin and deaminodiselenooxytocin) in 6 N HCl at 110° for 22 hr partially degraded selenocystine; however, when selenocystine itself was treated under identical reaction conditions it was almost entirely destroyed.

Evolution of neurophysin proteins: The partial sequence of human neurophysin-I

Neurophysins are a group of proteins found throughout the hypoth~amoneurohypophyseal system (e.g., [l-4] ) which are considered to function as carrier substances for the neurohypophyse~ hormones during transport from the hypothalamus and storage within the posterior pituitary [5]. Most mammalian species have two major neurophysins [6]. The complete amino acid sequence of one of the bovine neurophysins has been reported [7] and its covalent structure has been determined by the localization of all of its disulfide bonds [8]. In addition, the sequence of one of the porcine proteins has been described f9], and the sequence of the N-terminal 50 amino acid residues of the second bovine neurophysin has also been reported [lo] and a tentative assignment has been made through residue position 75 (Walter, Schlesinger, Breslow, Kehoe and Capra, unpublished). Foss et al. have recently described the isolation and amino acid sequence of the N-terminal 18 residues of a human neurophysin [ 111. This report concerns the further puri~cation of human neurophysin I and the determination of its N-terminal sequence through residue 54. The results are discussed in relationship to the evolution of this group of proteins.

Inactivation studies of angiotensin II by purified enzymes.

Die hochgereinigte Arylamidase vom Schweinehirn spaltet, im Gegensatz zur ebenfalls isolierten Säureprotease und Aminopeptidase, Ile5-Angiotensin II, wobei die ersten 5 N-terminalen Aminosäuren von hydrolytischen Enzymen freigesetzt werden.

STRUCTURE-ACTIVITY STUDIES OF MSH-RELEASE-INHIBITING HORMONE*

1. Introduction The release and inhibition of release of melanocyte- stimulating hormone (MSH) from rat pituitary are un- der the control of two hormonal factors present in the hypothalamus [ 11. Both are fragments of oxytocin re- sulting from an enzymic degradation of this neurohy- pophyseal hormone [2-51. It was established that the chemical structure of the MSH-release-inhibiting factor (MSH-R-IF) isH-Pro-Leu-Gly-NH, [3,4,6], and more recently we reported that the pentapeptide H- Cys-Tyr-Ile-Gln-Asn-OH (hereafter referred to as releasing peptide, R-p), possesses the capacity to re- lease pituitary MSH and increase MSH plasma levels

Arginine-vasopressin, lysine-vasopressin, and oxytocin, c14-labeled in the glycine residue

Die Synthese von Arginin-Vasopressin, Lysin-Vasopressin und Oxytocin, deren Glycinrest eine14C-Markierung trägt, wird mit Hilfe der Festkörpermethode nachMerrifield beschrieben.

Enzymic Cleavage of Post-Proline Peptide Bonds: Degradation of Arginine-Vasopressin and Angiotensin II

Summary A partially purified enzyme from human uterine tissue was found to cleave peptides specifically at the carboxyl side of proline residues when arginine-vasopressin, oxytocin, and Ile5-angiotensin II were tested as proline-containing substrates. The enzyme has a pH optimum of 7.4; its activity is not affected by Mn2+ or Mg2+ (10-6 to 10-3 M). The authors thank Dr. T. D. Kerenyi for his active participation and interest in this work. The technical help of Mrs. I. Mintz was appreciated.

Conformational constraints within neurohypophyseal hormones influencing the action of chymotrypsin

Abstract Intact oxytocin, lysine-vasopressin and arginine-vasopressin are resistant to the action of α-chymotrypsin when incubated at an enzyme-substrate ratio of 1:300. Conversely, the Tyr-Ile, Tyr-Phe or Phe-Gln peptide bonds in the corresponding acyclic, S-alkylated nonapeptides are efficiently hydrolyzed by α-chymotrypsin. These results show that the 20-membered ring component of the neurohypophyseal hormones, which was proposed to consist of a compact antiparallel β-pleated sheet conformation, presents an image to the enzyme differing significantly from that of the same amino acid residues present in a linear peptide. This prevents the enzyme from recognizing a potential substrate. Neurohypophyseal hormone analogs thought to possess a less constrained 20-membered ring structure are susceptible to cleavage of peptide bonds located in the cyclic moiety.