Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “AMIDES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 595 records · Page 33Linked to original sources
PubMed2007

The antagonistic metabolite of GLP-1, GLP-1 (9-36)amide, does not influence gastric emptying and hunger sensations in man.

OBJECTIVE: Glucagon-like peptide-1 (GLP-1 (7-36)amide) is an intestinal hormone that is released in response to meal ingestion. GLP-1 reduces postprandial gastric and exocrine pancreatic secretion and is believed to inhibit gastric emptying. Furthermore, GLP-1 may play a role in hunger and thirst regulation. In vivo, GLP-1 is rapidly (within minutes) converted into a metabolite, GLP-1 (9-36)amide, which has been shown to act as a GLP-1 receptor antagonist in vitro and in anaesthetized pigs. The purpose of this study was to assess the effect of infusion of GLP-1 (9-36)amide on hunger ratings and antral emptying of a meal. MATERIAL AND METHODS: Six healthy volunteers were tested in a double-blind, placebo-controlled fashion. Antral emptying of a liquid meal and hunger ratings were determined using ultrasound technology and visual analogue scale scoring during infusions of saline or GLP-1 (9-36)amide (5 pmol/kg body wt/min) resulting in supraphysiological concentrations. RESULTS: Infusion of GLP-1 (9-36)amide had no effect on gastric emptying or the sensation of hunger compared to saline. CONCLUSIONS: Our findings suggests that the rapid formation of the antagonistic metabolite does not influence gastric emptying and hunger ratings in humans even when it is present in supraphysiological concentrations.

Adult↗
PubMed2000

Vascular and endothelial actions of inhibitors of substance P amidation.

Formation of mature active neuropeptides such as substance P (SP) from their glycine extended precursors entails alpha-amidation of peptide precursors by the sequential enzymatic action of peptidylglycine alpha-monooxygenase (PAM) and peptidylamidoglycolate lyase (PGL). We reported that these two enzymes that can produce mature active neuropeptides are present in cultured bovine aortic endothelial cells (BAECs). We hypothesize that alpha-amidation of peptides occurs in endothelial cells and that these peptides are critically involved in the overall regulation of cardiovascular function. In this study, this hypothesis was tested using specific amidation inhibitors to determine their effects on the actions of SP and its glycine-extended precursor (SP-Gly). We have found that SP and SP-Gly are equipotent in stimulating nitric oxide (NO) release by BAECs. At 10(-5) M, the specific inhibitors of PAM (4-phenyl-3-butenoic acid; PBA) and PGL (5-acetamido-2,4-diketo-6-phenyl-hexanoic acid and its methyl ester) reduced NO basal release by 40, 34, and 45%, respectively. They also reduced the production of NO induced by SP-Gly by 63, 68, and 69%, respectively, but had no effect on NO production in response to either SP or acetylcholine. SP and SP-Gly also were equipotent in relaxing rat aortic segments. The vasorelaxation to SP-Gly was endothelium dependent and inhibited by the NOS antagonist L-nitroarginine methyl ester (L-NAME), but it was not affected by inhibition of prostaglandin synthesis. Inhibitors of both PAM and PGL significantly reduced the vasorelaxing actions of SP-Gly, whereas responses to SP were not affected. A cumulative infusion of PBA into the femoral artery of rabbits, at final concentrations of 2.4, 24, and 240 microM for 20 min each, increased the vascular resistance (VR), indicating the tonic production of vasodilating amidated peptide(s). This effect was maximum at 60 min after infusion (20.5 +/- 4.7 vs. 8.2 +/- 0.7 mm Hg/ml/min; p < 0.05). These results suggest that endothelial cells can produce mature SP from its SP-Gly precursor and that a product of peptide alpha-amidation tonically stimulates endothelial cell NO release to control vascular tone.

Amidine-Lyases↗
PubMed1992

Amide-Linked Indoleacetic Acid Conjugates May Control Levels of Indoleacetic Acid in Germinating Seedlings of Phaseolus vulgaris.

We have shown that amide-linked IAA (indole-3-acetic acid) conjugates accumulated to high levels during maturation of bean seeds (K. Bialek and J.D. Cohen [1989] Plant Physiol 91: 775-779). In the present study, we were interested in the fate of these and other IAA conjugates during seed germination. The content of amide-linked conjugates of IAA in cotyledons declined dramatically during the first hours of imbibition. The rate of decline slowed markedly during the period of the resumption of axis growth. The level of amide-linked IAA conjugates in cotyledons remained relatively high after almost 1 week of germination. The decline of IAA conjugates in cotyledons was followed by a steady increase in the content of both free and amide-linked IAA in the embryonic axes. Amide-linked IAA conjugates were also present in the axes cultured on agar after the cotyledons were removed, which suggests that de novo production of these IAA conjugates occurs in the axis of germinating bean seedlings. A comparison of relative amounts of free and conjugated IAA in the axes of intact seedlings and axes cultured on agar showed lower levels of free IAA and higher levels of conjugated IAA in much slower growing isolated axes. These results suggest a more general role for IAA conjugates in the control of seedling growth than simply to serve as a seed storage form of auxin.

Journal Article↗
PubMed1982

Influence of Protein Synthesis on NO(3) Reduction, NH(4) Accumulation, and Amide Synthesis in Suspension Cultures of Paul's Scarlet Rose.

Changes in the concentrations of NH(4) (+) and amides during the growth of suspension cultures of rose (Rosa cv. Paul's Scarlet) cells were examined. When cells were grown in medium possessing only NO(3) (-) as a nitrogen source, the concentrations of NH(4) (+) and amides increased to 4.0 x 10(-1) and 5.9 micromoles per gram fresh weight, respectively. The amounts of both constituents declined during the later stages of growth. When a trace amount of NH(4) (+) was added to the NO(3) (-) base starting medium, the concentration of NH(4) (+) in the cells was increased to 7.0 x 10(-1) micromoles per gram fresh weight.A comparison between the concentration of NH(4) (+) in the cells (4.3 x 10(-4) molar) with the K(m) values for glutamate dehydrogenase (5 x 10(-3) molar) and glutamine synthetase (1.7 x 10(-5) molar) showed that the endogenous NH(4) (+) would have to be concentrated 10-fold in compartments possessing glutamate dehydrogenase in order for the substrate to reach one-half the saturation level for that enzyme.The influence of protein synthesis on the level of NH(4) (+) and amides was examined by blocking protein synthesis with cycloheximide or puromycin and measuring changes in NH(4) (+) and amide concentration over the subsequent 4 hours. The level of both NH(4) (+) and amides showed substantial increases when protein synthesis was blocked. Ammonium accumulated to concentrations surpassing those reported by other authors to be toxic to plants. The reduction of NO(3) (-) did not appear to be influenced by the blockage of protein synthesis.

Journal Article↗
PubMed1984

Amino Acid metabolism in pea leaves : utilization of nitrogen from amide and amino groups of [N]asparagine.

The flow of nitrogen from the amino and amide groups of asparagine has been followed in young pea (Pisum sativum CV Little Marvel) leaves, supplied through the xylem with (15)N-labeled asparagine. The results confirm that there are two main routes for asparagine metabolism: deamidation and transamination.Nitrogen from the amide group is found predominantly in 2-hydroxy-succinamic acid (derived from transamination of asparagine) and in the amide group of glutamine. The amide nitrogen is also found in glutamate and dispersed through a range of amino acids. Transfer to glutamineamide results from assimilation of ammonia produced by deamidation of both asparagine and its transamination products: this assimilation is blocked by methionine sulfoximine. The release of amide nitrogen as ammonia is greatly reduced by aminooxyacetate, suggesting that, for much of the metabolized asparagine, transamination precedes deamidation.The amino group of asparagine is widely distributed in amino acids, especially aspartate, glutamate, alanine, and homoserine. For homoserine, a comparison of N and C labeling, and use of a transaminase inhibitor, suggests that it is not produced from the main pool of aspartate, and transamination may play a role in the accumulation of homoserine in peas.

Journal Article↗
PubMed1989

Synthesis, characterization and inhibitory activities of (4-N3[3,5-3H]Phe10)PKI(6-22)amide and its precursors: photoaffinity labeling peptides for the active site of cyclic AMP-dependent protein kinase.

PKI(6-22)amide is a 17 residue peptide corresponding to the active portion of the heat-stable inhibitor of cAMP-dependent protein kinase. The peptide is a potent (Ki = 1.6 nM), competitive inhibitor of the enzyme. The photoreactive peptide analog (4-azidophenylalanine10)PKI(6-22)amide was synthesized in both its non-radiolabeled and tritiated forms by chemical modification of precursor peptides that were prepared by stepwise solid-phase synthesis. (4-Amino[3,5-3H]phenylalanine10)PKI(6-22)amide, the precursor for the radiolabeled arylazide peptide, was obtained by catalytic reduction of the corresponding peptide containing the 3,5-diiodo-4-aminophenylalanine residue at position 10. The purified PKI peptides were analyzed by HPLC, amino acid analysis, and u.v. spectra. In the dark, (4-azidophenylalanine10)PKI(6-22)amide inhibited the catalytic subunit of cAMP-dependent protein kinase with a Ki value of 2.8 nM. The photoreactivity of the arylazide peptide was demonstrated by time-dependent u.v. spectral changes on exposure to light. Photolysis of the catalytic subunit (4-azido[3,5-3H]phenylalanine10)PKI(6-22)amide complex resulted in specific covalent labeling of the enzyme. The data indicate that this peptide is a useful photoaffinity labeling reagent for the active site of the protein kinase.

Affinity Labels↗
PubMed1990

Backbone modifications in cyclic peptides. Conformational analysis of a cyclic pseudopentapeptide containing a thiomethylene ether amide bond replacement.

NMR and X-ray crystallographic studies have shown that cyclic pentapeptides of the general structure cyclo(D-Xxx-Pro-Gly-Pro-Gly) possess beta- and gamma-turn intramolecular hydrogen bonds. As part of our continuing series surveying the compatibility of various amide bond replacements on peptide structure, we have synthesized cyclo(D-Phe-Pro psi[CH2S]Gly-Pro-Gly). The pseudopeptide was prepared by solid phase methods and cleaved from the resin by a new procedure involving phase transfer catalysis using K2CO3 and tetrabutylammonium hydrogen sulfate. Cyclization was carried out with the use of DPPA, HOBt, and DMAP to afford the product in 69% yield. The conformational behavior of the pseudopeptide was analyzed by 1H and 13C (1D and 2D) NMR techniques. The backbone modification replaced the amide bond that is involved in a gamma-turn intramolecular hydrogen bond in the all-amide structure. In CDCl3, the pseudopeptide adopted the same all-trans conformation as its parent, although the remaining beta-turn hydrogen bond was weaker according to delta delta/delta TNH measurements. In DMSO-d6, the all-trans conformer and a second conformer were observed in a ratio of 55:45. These conformers, which slowly interconverted on the NMR time scale, could be separately assigned; peaks due to chemical exchange were readily distinguishable by the ROESY technique as reported earlier by others. 13C and ROESY experiments suggested the minor conformer contained one cis amide bond at the Gly1-Pro2 position. Thus, both the location and type of amide surrogate are important determinants affecting the compatibility of the replacement with a particular conformational feature.

Amino Acid Sequence↗
PubMed1992

Preparation of protected peptide amides using the Fmoc chemical protocol. Comparison of resins for solid phase synthesis.

Different resins were examined for their potential use in the solid phase synthesis of protected peptide amides using the 9-fluorenylmethoxycarbonyl (Fmoc) chemical protocol. The model protected peptide amide BocTyr-Gly-Gly-Phe-Leu-Arg(Pmc)NH2 (1) was synthesized on both the acid-labile 4-(2',4'-dimethoxyphenyl-Fmoc-aminomethyl)phenoxy resin (Rink amide resin) (2) and on resins containing the base-labile linker 4-hydroxymethylbenzoic acid. Of the resins examined only the methylbenzhydrylamine resin containing the 4-hydroxymethylbenzoic acid linkage, which was cleaved by ammonolysis in isopropanol, gave the model peptide 1 in good overall yield (53% including functionalization). Thus the synthesis of protected peptide amides by solid phase synthesis using Fmoc-protected amino acids with t-butyl-type side chain protecting groups is feasible. The choice of peptide-resin linkage and its cleavage conditions, however, are critical to the success of such syntheses. The potential application of this synthetic strategy to the preparation of novel peptide amides is discussed.

Amino Acid Sequence↗
PubMed1990

Amylin-amide: a new bone-conserving peptide from the pancreas.

Amylin-amide is a new member of the family of peptides encoded by the calcitonin multigene complex. In the present study, we have compared directly, the hypocalcaemic potency and duration of action of human amylin-amide and human calcitonin in an in vivo rat bioassay and an in vitro osteoclast bone resorption assay. Amylin-amide was found to have a potency approximately 40-fold lower than human calcitonin, whilst both peptides followed the same time course. This suggests that amylin-amide is the most potent non-calcitonin hypocalcaemic peptide so far reported. An important physiological implication follows. It would seem that amylin-amide can play a central role in the maintenance of the skeleton by virtue of its inhibitory influence on osteoclastic function.

Amyloid↗
PubMed1998

Effect of peptide binding on amide proton exchange rates in the PDZ2 domain from human phosphatase hPTP1E.

Amide hydrogen-deuterium exchange rates were measured in the PDZ2 domain from human phosphatase hPTPIE by 1H-15N heteronuclear NMR spectroscopy. Protection factors were calculated for the slowly exchanging hydrogens in both the free PDZ2 domain and its complex with an octapeptide peptide, R-N-E-I-Q-S-L-V, derived from the C-terminus of the Fas receptor. Aside from a short alpha-helical region alpha1 (amino acids A-45 to D-49), the pattern of highly protected amides correlated well with the presence of hydrogen bonds in elements of the secondary structure. Hydrogen-bonded amides showed relatively fast exchange rates with half-lives of less than 9 h at pD 7.6 and 8 degrees C. Protection factors, calculated as the ratio of theoretical (denatured) and observed exchange rates, showed less dispersion in maximal values than did the actual exchange rates. This behavior and the large pH dependence of the exchange rates suggest that amide exchange is close to the EX2 limit. In this limit, exchange of the most protected amides occurs through a global unfolding mechanism. The free energy of the unfolding calculated from the largest protection factors is 4.8 +/- 0.4 kcal/mol (1 cal = 4.184 J). This deltaG(o) closely matches the value measured by experiments with guanidine hydrochloride and fluorescence emission spectroscopy. Peptide binding to PDZ2 resulted in mostly global effects and stabilized the folded domain by 1.4 kcal/mol.

Deuterium↗
PubMed1992

Differential intestinal deconjugation of taurine and glycine bile acid N-acyl amidates in rats.

Mechanisms responsible for the difference in the relative amounts of taurine- and glycine-conjugated bile acid N-acyl amidates (Tau/Gly ratio) are not fully understood. In the present study, the stability of taurine- and glycine-conjugated bile acid N-acyl amidates during intestinal transit and absorption was examined to investigate the contribution of intestinal deconjugation to the Tau/Gly ratio in rat bile. Radiolabeled chenodeoxycholic acid (CDC) and its N-acyl amidates with glycine (CDC-Gly) or taurine (CDC-Tau) were introduced into the lumen of the upper small intestine in the biliary fistula rats, and radioactive metabolites in bile, blood, urine, and tissues were identified and quantitated by high-performance liquid chromatography. Results indicated that 1) extensive deconjugation of CDC-Gly occurs during intestinal absorption; 2) CDC-Tau is recovered in bile largely intact; and 3) newly synthesized CDC-Tau and CDC-Gly are formed in a ratio of less than 2:1 after administration of [14C]-CDC. In summary, the present study demonstrates that resistance of taurine-conjugated bile acid N-acyl amidates to hydrolysis in the intestine, rather than a difference in synthesis of taurine- and glycine-conjugated N-acyl amidates in liver, may account for the high Tau/Gly ratio in rat bile.

Animals↗
PubMed1996

Organization of GnRH and FMRF-amide systems in two primitive bony fishes (order polypteriformes).

To investigate the evolution of the neural organization of gonadotropin-releasing hormone (GnRH), we have examined GnRH-immunoreactivity in two brachiopterygian fishes (Polypterus palmas and Calamoichthys calabaricus). Distal regions of the terminal nerve (TN) within the medial olfactory nerve contained clusters of GnRH-immunoreactive (ir) perikarya (< 10 microns). More proximal, isolated GnRH-ir neurons were present among TN fascicles as they penetrated the ventral forebrain, and a few ir neurons were observed accompanying GnRH-ir fibers in the rostromedial telencephalon. GnRH-ir neurons were not observed in the preoptic area or ventral hypothalamus. In contrast, a small group of GnRH-ir neurons was localized in the periventricular nucleus of the posterior tuberculum. GnRH-ir fibers were present in widespread areas of the brain, including the olfactory bulb, telencephalon, optic nerve, hypothalamus, thalamus, habenula, optic tectum, tegmentum, pituitary and spinal cord. To further characterize projections of TN neurons, we utilized antiserum to FMRF-amide, a small peptide produced by TN cells in other vertebrates. Perikarya that were FMRF-amide-ir within the TN were similar in distribution to GnRH-TN neurons, and the distribution of FMRF-amide-ir fibers overlapped those of GnRH-ir fibers, thus providing a useful marker for identifying TN projections. An additional population of FMRF-amide-ir neurons was present in the periventricular hypothalamus. Our results suggest that in the polypteriformes, GnRH and FMRF-amide neurons of the TN are similar to those observed in other vertebrates; however, the paucity of GnRH cells in the basal forebrain may be unique to primitive actinopterygians and elasmobranchs, and may result from the lack of migration of GnRH neurons into the forebrain, a phenomenon that likely occurs in all other vertebrate classes. Finally, the identification of GnRH-ir neurons in the posterior tuberculum is consistent with similar, and perhaps homologous, GnRH neurons present in nearly all other vertebrate classes.

Animals↗
PubMed2007

Identification of fatty acids and fatty acid amides in human meibomian gland secretions.

PURPOSE: The complex superficial lipid layer of the tear film functions to prevent evaporation and maintain tear stability. Although classes of lipids found in the tear film have been reported, individual lipid species are currently being studied with more sophisticated. METHODS: The purpose of this work was to show the identification of fatty acids and the fatty acid amides in human meibomian gland secretions by using electrospray mass spectrometry. methods. Human meibomian gland secretions (meibum) were analyzed by electrospray quadrupole time-of-flight mass spectrometry (positive- and negative-ion mode). Accurate mass determination and collision-induced dissociation of meibum, and lipid standards were used to identify lipid species. RESULTS: Mass analysis of meibum in an acidic chloroform-methanol solution in positive-ion mode revealed a mass peak of m/z 282.3, which was identified as the protonated molecule of oleamide [C(18)H(35)NO+H](+). The high-resolution mass analysis of the m/z 282.2788 peak (oleamide) demonstrated a mass accuracy of 3.2 parts per million (ppm). Collision-induced dissociation of this species from meibum, compared with an oleamide standard, confirmed its identification. Myristic, palmitic, stearic, and oleic free fatty acids were identified in a similar manner, as were the other fatty acid amides (myristamide, palmitamide, stearamide, and erucamide). CONCLUSIONS: The findings indicate that oleamide (cis-9-octadecenamide), an endogenous fatty acid primary amide, is a predominant component of meibum when examined by electrospray mass spectrometry. The novel finding of oleamide and other members of the fatty acid amide family in the tear film could lead to additional insights into the role of fatty acid amide activity in human biological systems and may indicate a new function for this lipid class of molecules in ocular surface signaling and/or in the maintenance of the complex tear film.

Bodily Secretions↗
PubMed1989

The erythrocyte as instigator of inflammation. Generation of amidated C3 by erythrocyte adenosine deaminase.

Myocardial ischemia is characterized by the liberation of adenosine and by complement-mediated inflammation. We have reported that amidated C3, formed when ammonia (NH3) disrupts the thiolester bond of C3, serves as an alternative pathway convertase, generates C5b-9, and stimulates phagocytic oxidative metabolism. We investigated whether the deamination of adenosine by adenosine deaminase in hematopoietic cells might liberate sufficient ammonia to form amidated C3 and thereby trigger complement-mediated inflammation at ischemic sites. In the presence of 4 mM adenosine, NH3 production per erythrocyte (RBC) was equal to that per neutrophil (PMN) (3.3 X 10(-15) mol/cell per h). Because RBC outnumber PMN in normal blood by a thousandfold, RBC are the major source of NH3 production in the presence of adenosine. NH3 production derived only from the deamination of adenosine by the enzyme adenosine deaminase and was abolished by 0.4 microM 2'-deoxycoformycin, a specific inhibitor of adenosine deaminase. When purified human C3 was incubated with 5 X 10(8) human RBC in the presence of adenosine, disruption of the C3 thiolester increased more than twofold over that measured in C3 incubated with buffer, or in C3 incubated with RBC (P less than 0.05). The formation of amidated C3 was abolished by the preincubation of RBC with 2'-deoxycoformycin (P less than 0.001). Amidated C3 elicited statistically significant release of superoxide, myeloperoxidase, and lactoferrin from PMN. Thus, the formation of amidated C3 by RBC deamination of adenosine triggers a cascade of complement-mediated inflammatory reactions.

Adenosine↗
PubMed2002

Immunocytochemical finding of the amidating enzymes in mouse pancreatic A-, B-, and D-cells: a comparison with human and rat.

alpha-Amidation is catalyzed by two enzymatic activities, peptidyl-glycine alpha-hydroxylating mono-oxygenase (PHM) and peptidyl-alpha-hydroxyglycine alpha-amidating lyase (PAL), denoted collectively as peptidyl-glycine alpha-amidating mono-oxygenase (PAM), which also may include transmembrane and cytoplasmic domains. PAM is present in mammalian pancreas, where it appears to be abundant in the perinatal period. Nevertheless, there is no agreement on the cell type(s) that produces PAM or even on its presence in adults. In the present study we found PAM (PHM and cytoplasmic domain) immunoreactivity (IR) in A-, B-, and D-cells of adult mouse pancreas. In contrast to previous reports, PAM IR was found in B-cells of human and rat. Most of the B/D-cells were PAM immunoreactive, although with variable intensity, whereas less than half of A-cells displayed IR. Immunocytochemistry and Western blotting suggested the existence of different PAM molecules. Differences in the cellular distribution of IR for PAM domains were also observed. Whereas PHM-IR was extended throughout the cytoplasm in the three cell types, presumably in the secretory granules, IR for the cytoplasmic domain in A/D-cells was restricted to a juxtanuclear region, perhaps indicating its cleavage in Golgi areas. Although glucagon, insulin, and somatostatin are non-amidated, amidated peptides (glucagon-like peptide 1, adrenomedullin, proadrenomedullin N-terminal 20 peptide) were found in the three cell types.

Animals↗
PubMed1998

Peptide-amidating enzymes are expressed in the stellate epithelial cells of the thymic medulla.

C-terminal amidation is a post-translational processing step necessary to convey biological activity to a large number of regulatory peptides. In this study we have demonstrated that the peptidyl-glycine alpha-amidating monooxygenase enzyme complex (PAM) responsible for this activity is located in the medullary stellate epithelial cells of the thymus and in cultured epithelial cells bearing a medullary phenotype, using Northern blot, immunocytochemistry, in situ hybridization, and enzyme assays. Immunocytochemical localization revealed a granular pattern in the cytoplasm of the stellate cells, which were also positive for cytokeratins and a B-lymphocyte-associated antigen. The presence of PAM activity in medium conditioned by thymic epithelial cell lines suggests that PAM is a secreted product of these cells. Among the four epithelial cell lines examined, there was a direct correlation between PAM activity and content of oxytocin, an amidated peptide. Taken together, these data provide convincing evidence that thymic epithelial cells have the capacity to generate amidated peptides that may influence T-cell differentiation and suggest that the amidating enzymes could play an important role in the regulation of thymic physiology.

Animals↗
PubMed1993

Immunocytochemical localization of peptidylglycine alpha-amidating monooxygenase enzymes (PAM) in human endocrine pancreas.

We studied the distribution of the enzymes that are involved in the post-translational alpha-amidation of regulatory peptides in human endocrine pancreas, using immunocytochemical methods for light and electron microscopy. Immunoreactivity for the two enzymes involved, peptidylglycine alpha-hydroxylating monooxygenase (PHM) and peptidyl-alpha-hydroxyglycine alpha-amidating lyase (PAL), was located in the periphery of the islets of Langerhans and in ductal endocrine cells. Staining of reverse-face serial sections demonstrated that these immunoreactivities co-localize with glucagon but not with pancreatic polypeptide (PP), insulin, or somatostatin. Double immunogold staining for electron microscopy confirmed the previous results and revealed a different localization for each enzyme inside the secretory granule: PHM is present in the central core of the glucagon-containing granules, whereas PAL is predominantly located near the granule membrane. The existence of an amidated peptide, GLP1, in the A-cells explains the presence of peptidylglycine alpha-amidating monooxygenase enzymes (PAM) in these cells. The absence of the enzymes in the PR-cells raises the possibility that a different form of amidating enzyme may be involved in the post-translational processing of this peptide.

Amidine-Lyases↗
PubMed1996

Distribution of peptidyl-glycine alpha-amidating mono-oxygenase (PAM) enzymes in normal human lung and in lung epithelial tumors.

C-terminal alpha-amidation is a post-translational modification necessary for the biological activity of many regulatory peptides produced in the respiratory tract. This modification is a two-step process catalyzed by two separate enzyme activities, both derived from the peptidyl-glycine alpha-amidating mono-oxygenase (PAM) precursor. The distribution of these two enzymes, peptidyl-glycine alpha-hydroxylating monoxygenase (PHM) and peptidyl-alpha-hydroxyglycine a amidating lyase (PAL), was studied in the normal lung and in lung tumors using immunocytochemical methods and in situ hybridization. In normal lung the enzymes were located in some cells of the airway epithelium and glands, the endothelium of blood vessels, some chondrocytes of the bronchial cartilage, the alveolar macrophages, smooth muscle cells, neurons of the intrinsic ganglia, and in myelinated nerves. A total of 24 lung tumors of seven different histological types were studied. All cases contained PAM-immunoreactive cells with various patterns of distribution. All immunoreactive cells were positive for the PHM antiserum but only some of them for the PAL antiserum. The distribution of PAM co-localizes with some other previously described amidated peptides, suggesting that amidation is an important physiological process taking place in the normal and malignant human lung tissue.

Aged↗