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Biomedical subjects

A M Gibson

Publications and source records attributed to A M Gibson.

40 records · Page 3Linked to original sources
PubMedDate not supplied

Thyrotrophin releasing hormone degradation by rat synaptosomal peptidases: production of the metabolite His-Pro.

The dipeptide, His-Pro, is the major product of the degradation of TRH by rat synaptic membranes in vitro. A small amount of His-Pro is also formed from TRH by the synaptosomal soluble fraction. From inhibitor studies, the main route to His-Pro appears to involve removal of the pGlu residue by membrane-bound metal-dependent pyroglutamylaminopeptidase followed by deamidation. The deamidation step is not mediated by proline endopeptidase (EC3.4.21.26) nor dipeptidylpeptidase-IV (EC3.4.14.5) since it is insensitive to bacitracin and diprotin-A, and may therefore involve a novel membrane-bound TRH metabolizing enzyme. His-Pro is degraded rapidly by the soluble synaptosomal fraction, presumably by prolidase (EC3.4.13.9) and more slowly by the synaptic membrane fraction.

Animals↗
PubMedDate not supplied

Specificity of action of human brain alanyl aminopeptidase on Leu-enkephalin and dynorphin-related peptides.

The major cystosolic aminopeptidase (alanylaminopeptidase) was purified to homogeneity from human cerebral cortex and the specificity of its actions on a series of Leu-enkephalin-related peptides of increasing chain length was determined. In each case, only the N-terminal Tyr-Gly bond was hydrolysed. Kinetic analysis of the data revealed that the specificity constant (kcat/Km;s-1M-1) falls with increasing chain length from a maximum of 13.6 x 10(4) for Leu-enkephalin (5 residues) to 5.8 x 10(2) for dynorphin (1-13). Dynorphin 1-17, while not being degraded itself acted as a competitive inhibitor (Ki = 2.7 microM) of the degradation of smaller peptides. Beta-endorphin was not hydrolysed by analylaminopeptidase, nor did it act as an inhibitor of the enzyme.

Aminopeptidases↗
PubMedDate not supplied

Removal of Arg1 and Phe22 from CLIP (ACTH18-39) by rodent pituitary and blood peptidases.

The major product on incubation of CLIP (ACTH18-39) with rat and mouse serum, rat plasma and whole blood, and soluble extracts of rat pituitary is [des-Arg1]-CLIP (ACTH19-39) while [des-Phe22]-CLIP (ACTH18-38) is the major product with pituitary particulate fraction. In both cases, p-chloromercuribenzoate-sensitive, metal-dependent peptidase activity appears to be responsible for the cleavage. The serum enzyme may be related to proline aminopeptidase. Material coeluting with [des-Arg]-CLIP on two HPLC solvent gradients is present in the superfusion media from neurointermediate lobes of genetically obese (ob/ob) mice but is not present in acid extracts of the lobe. This suggests that postsecretory processing of CLIP may involve removal of the N-terminal Arg residue.

Adrenocorticotropic Hormone↗