Biodegradation of Luteinizing Hormone-Releasing Hormone

Nikolics, Károly; Kéri, Gÿorgý; Szőke, Balázs; Horváth, Anikó; Teplán, István

doi:10.1007/978-1-4615-9248-8_20

Cited by 5 publications

(1 citation statement)

References 61 publications

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“…In contrast to other reports [29, 301, no evidence for a plasma-membrane-bound enzyme could be obtained, but we cannot exclude the possibility that such an enzyme has been irreversibly inactivated or lost during the preparation of the subcellular fractions. Experiments with intact cells in culture, however, also indicate the lack of plasma-membrane-bound enzymes capable of hydrolyzing gonadoliberin and suggest the existence of other inactivation mechanisms [31] (and unpublished work, performed in collaboration with Dr Carl Denef, Leuven, Belgium). Interestingly, gonadoliberin is apparently not a substrate for the plasma-membrane-bound thermolysin-like metalloendopeptidase, which hydrolyzes peptide bonds at the amino side of hydrophobic amino acids, and the thyroliberin-degrading enzyme, which cleaves the tripeptide at the <Glu-His peptide bond.…”

Section: Discussionmentioning

confidence: 89%

Subcellular distribution of particle-bound neutral peptidases capable of hydrolyzing gonadoliberin, thyroliberin, enkephalin and substance P

et al. 1984

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Subcellular fractions from rat anterior pituitary homogenates were obtained by differential and gradient centrifugation, identified with the help of marker enzymes and screened for peptidases capable of hydrolyzing gonadoliberin, thyroliberin, enkephalin and substane P. Since each neuropeptide is susceptible to cleavage by more than one enzyme, specific substrates or inhibitors have been used for the selective determination of the individual peptidasic activities. Among the various enzymes tested, the angiotensin‐converting enzyme, the thermolysin‐like metalloendopeptidase (‘enkephalinase’), a thyroliberin‐degrading enzyme and some aminopeptidasic activities were found to be associated with the plasmamembrane. Other aminopeptidases, a gonadoliberin‐degrading and a substance‐P‐degrading enzyme are associated with the mitochondria and thus are most likely not involved in the biological inactivation of neuropeptides.

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Section: Discussionmentioning

confidence: 89%

Subcellular distribution of particle-bound neutral peptidases capable of hydrolyzing gonadoliberin, thyroliberin, enkephalin and substance P

et al. 1984

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Ultrastructural characterization of gonadotropin‐releasing hormone (GnRH)‐producing neurons

Jennes

Stumpf

Sheedy

1985

J of Comparative Neurology

101

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By means of preembedding immunohistochemistry, two types of gonadotropin-releasing hormone (GnRH) positive neurons in the rat could be identified and characterized in the preoptic region and in the diagonal band: (1) a "smooth" GnRH neuron with relatively even cytoplasmic contours, and (2) a "spiny" GnRH neuron with thorn-like protrusions of the perikaryon and cell processes. Both cell types contain the same organelles in similar number and distribution, but they differ in the number of synaptic contacts. In general, GnRH cell bodies have a large round or ovoid nucleus, well-developed rough endoplasmic reticulum arranged in multilayered stacks or as individual cisternae, and several Golgi complexes. Lysosomes are not numerous under the conditions studied. Specializations include kinocilia, nematosomes, and lamellar whorls. Throughout the cytoplasm, scattered dense core vesicles with a diameter of 100 nm and clear vesicles with a diameter of 30-40 nm can be seen with a preferential localization close to the cell membrane. The cell processes of smooth GnRH cells close to the perikaryal appear as extensions of the perikaryal cytoplasm with all organelles except the nucleus. The two neurites originate from the perikaryon as tapering cones over a distance of 200-300 micron, until they reach a diameter of 0.5-3 micron. Cell processes of spiny GnRH cells show bifurcations, protrusions, or invaginations and contain clear and dense core vesicles in their spines. In areas distant from the perikaryon, immunoreactive fibers with a large number of dense core and clear vesicles can occasionally be seen to terminate synaptically or asynaptically on other neurons. The GnRH neurons show postsynaptic specializations at the level of the perikaryon and at cell processes, when apposed by a presynaptic terminal. Such synaptic contacts are seen less frequently on smooth cells than on spiny cells. Large areas of the GnRH cell may be covered by a thin glial lamella, which separates the cell body from the surrounding neuropil. The results indicate the existence of two populations of GnRH cell bodies with different patterns of innervation, which suggest different integrative capacities.

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Pharmacokinetics and Metabolism of LHRH Analogs

Chan¹,

Nerenberg²

1987

LHRH and Its Analogs

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Biodegradation of Luteinizing Hormone-Releasing Hormone

Cited by 5 publications

References 61 publications

Subcellular distribution of particle-bound neutral peptidases capable of hydrolyzing gonadoliberin, thyroliberin, enkephalin and substance P

Subcellular distribution of particle-bound neutral peptidases capable of hydrolyzing gonadoliberin, thyroliberin, enkephalin and substance P

Ultrastructural characterization of gonadotropin‐releasing hormone (GnRH)‐producing neurons

Pharmacokinetics and Metabolism of LHRH Analogs

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