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Biomedical subjects

M Benuck

Publications and source records attributed to M Benuck.

At least 37 records · Page 2Linked to original sources
PubMed1986

Effect of several amino acid phosphonates and other compounds on rat brain and kidney peptidases.

A series of N-terminal phosphonate derivatives, H2O3PCHPhNHR (R = Leu, Phe, Trp, and/or Tyr), were synthesized with the aim of mimicking phosphoramidon, a potent inhibitor of enkephalinase, while avoiding the lability of the scissile P-N bond. All of the N-phosphonobenzyl derivatives of the amino acids, including the substituted succinylhydrazobenzophenone compounds, were inactive toward rat brain aminopeptidase and rat kidney carboxypeptidase. The N-monobenzylphosphonobenzyl derivatives, PhCH2OPO(OH)CHPhNHR, of individual amino acids and several of the N-phosphonobenzyl dipeptides showed inhibition in the micromolar range toward the soluble exopeptidase but were inactive with both the brain and kidney endopeptidase.

Aminopeptidases↗
PubMed1985

Proteolytic activity in brains of rabbits treated with aluminum.

Aluminum injection in rabbits leads to neurofibrillary changes which are at light microscopic level similar to those found in Alzheimer's disease. We used this animal model to see whether changes in proteolytic activity occur that may affect protein degradation in the altered neurofibrillary structure. Rabbits were injected via the cisterna magna with aluminum chloride, and after ten days tissue was excised from the spinal cord, hippocampus, occipital lobe, and cerebellum. Sections from the hippocampus and spinal cord were examined for neurofibrillary changes; enzyme activity was measured in all four areas. The enzymes studied were cathepsins A, B, and D, and the angiotensin-converting enzyme. No significant differences could be established in enzymatic activity in aluminum-injected animals compared to controls. However, a significant decrease in Triton-soluble proteins was observed in the treated animals, which correlated with changes in neurofibrillary structure. This decrease was most noticeable in the spinal cord (from 16.6 to 12.5 mg/g).

Aluminum↗
PubMed1984

Membrane-bound enzymes and their role in processing of the dynorphins and of the proenkephalin octapeptide Metenkephalin-Arg-Gly-Leu.

Synaptosomal membrane (SPM) bound exo- and endopeptidases cleave the dynorphins and Met-enkephalin-Arg-Gly-Leu at several sites to produce shorter fragments; among these are dynorphin 1-8 from 1-17, and Met-enkephalin from Met-enkephalin-Arg-Gly-Leu. The most vulnerable site is the Tyr-Gly bond cleaved by membrane-bound aminopeptidase(s), with the shorter peptides degraded more rapidly than the longer ones. A purified metalloendopeptidase sensitive to phosphoramidon inactivates the shorter peptide sequences at the Gly3-Phe4 bond, and the 1-13 and 1-17 sequences also at the Arg7-Ile8 bond. The kcat/Km ratios for purified metalloendopeptidase were 20-30 times higher for Leu-enkephalin and the proenkephalin octapeptide than for dynorphins 1-8, 1-13, and 1-17. Dynorphins 1-13 and 1-17 may serve as precursors for the widely distributed CNS neuropeptide dynorphin 1-8 since they were cleaved by a separate SPM endopeptidase insensitive to phosphoramidon. SPM monocarboxypeptidase converted dynorphin 1-13 to 1-12 (release of Lys) and dipeptidyl carboxypeptidase converted dynorphin 1-8 to 1-6; enkephalin octapeptide served as a precursor of Met-enkephalin by sequential action (release of Leu and Arg-Gly) of both carboxypeptidases.

Animals↗
PubMed1981

Peptide processing in the central nervous system.

1. A thiol proteinase from human pituitaries was purified approximately 400 fold and shown to have different chromatographic properties from that of calf brain. Among substrates cleaved were myelin basic protein, histones, beta-lipotropin, neurophysin, and Substance P. 2. The enzyme showed properties associated with a cathepsin-B like enzyme: dependence on -SH groups, pH optimum of 6.5, inhibition by leupeptin and a synthetic analog, Boc-D-Phe-Pro-arginal, and cleavage of dipeptidyl arylamides with basic residues adjacent to or penultimate to the chromatographic grouping. 3. Membranes present in the P2 fraction of rat brain contained three or more enkephalinases when submitted to DEAE-cellulose chromatography. Further purification on an IgG-Sepharose affinity column prepared with antibody to lung angiotensin converting enzyme indicated the presence of dipeptidyl carboxypeptidase(s) with properties distinct from those of ACE. In addition, the DEAE-cellulose fractions contained various aminopeptidase activities when tested with Leu-Gly-Gly, Leu-Nap, and Ala-Ala-Nap as substrates.

Animals↗
PubMed1980

Specificity of brain cathepsin D: cleavage of model peptides containing the susceptible Phe-Phe regions of myelin basic protein.

Brain cathepsin D, purified by affinity chromatography on Sepharose pepstatin columns, was incubated with synthetic peptides corresponding to the susceptible regions of the myelin basic protein encompassing the two Phe-Phe bonds. One peptide, Leu-Gly-Arg-Phe-Phe-Gly-Gly, was cleaved by cathepsin D at the Phe-Phe bond while another, Val-His-Phe-Phe-Lys-Asn-Gly, was resistant to cleavage. To determine if this was a result of His flanking the Phe-Phe bond, or chain length on the N-terminal side, two decapeptides were synthesized differing only in the presence or absence of His adjacent to Phe. The results show that both of the decapapetides were cleaved by cathepsin D at the Phe-Phe linkages. In addition, prolonged incubation led to release of N-terminal Lys, indicating an additional cleavage at the Phe-Lys bond. In contrast to the limited cleavage by cathepsin D, pepsin split all four peptides. These results support earlier work on the limited proteolysis of basic protein at the Phe-Phe bond and suggest additional sites upon prolonged exposure. Such peptides may have utility as alternative substrates for basic protein or as models for subsequent synthesis of possible inhibitors of the enzyme.

Amino Acid Sequence↗
PubMed1979

Degradation of luteinizing hormone-releasing hormone (LHRH) by brain prolyl endopeptidase with release of des-glycinamide LHRH and glycinamide.

A highly purified preparation of rabbit brain prolyl endopeptidase cleaved the decapeptide luteinizing hormone-releasing hormone (LHRH) at the ProGly . NH2 bond leading to the release within 1-3 h incubation at 37 degrees C of des-glycinamide LHRH and glycinamide. Evidence for this site of cleavage was obtained by the detection of glycinamide or glycine and groups by a microdanyslation procedure, and by separation of the breakdown products by high performance liquid chromatography (HPLC) on a revers phase C-18 column. Incubation led to the appearance of two new peaks as detected by HPLC one of which was collected and shown to have the composition consistent with des-glycinamide LHRH. The other peak ran in the position identical to that of authentic glycinamide. Results suggest that prolyl endopeptidase could play a role in the inactivation of LHRH in vivo.

Animals↗