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M Orlowski

Publications and source records attributed to M Orlowski.

162 records · Page 9Linked to original sources
PubMed1970

The gamma-glutamyl cycle: a possible transport system for amino acids.

Evidence is presented that rat kidney contains enzymes that catalyze the synthesis and utilization of glutathione; these reactions, which involve the uptake and release of amino acids from gamma-glutamyl linkage, constitute a cyclical process which is termed "the gamma-glutamyl cycle." The gamma-glutamyl cycle has properties that fulfill the requirements of an amino acid transport system. Thus, gamma-glutamyl transpeptidase may function in translocation and gamma-glutamylcysteine synthetase and glutathione synthetase may catalyze energy-requiring "recovery" steps in transport. These and other considerations suggest that glutathione serves a carrier function in amino acid transport.

Amino Acids↗
PubMedDate not supplied

Evidence that enzymatic conversion of N-[1(R,S)-carboxy-3-phenylpropyl]-Ala-Ala-Phe-p-aminobenzoate, a specific inhibitor of endopeptidase 24.15, to N-[1(R,S)-carboxy-3-phenylpropyl]-Ala-Ala is necessary for inhibition of angiotensin converting enzyme.

N-[1(R,S)-Carboxy-3-phenylpropyl]-Ala-Ala-Phe-p-aminobenzoate (cFP-AAF-pAB) is a potent, substrate-related, specific inhibitor of endopeptidase 24.15, an enzyme involved in the metabolism of bioactive peptides including bradykinin, neurotensin, and proenkephalin, and prodynorphin-derived enkephalin precursors. The observation that this inhibitor causes a pronounced decrease in blood pressure after intravenous infusion into normotensive rats posed the question of the mechanism of this hypotensive response. It was suggested previously that cFP-AAF-pAB is an inhibitor of angiotensin converting enzyme (ACE) and that this function can account for the hypotensive response to the inhibitor. We present here evidence that cFP-AAF-pAB has no intrinsic ACE-inhibitory activity. The previously observed inhibition is shown to be dependent on cleavage of the Ala-Phe bond in the inhibitor by endopeptidase 24.11 (enkephalinase, EC 3.4.24.11), a contaminant of some ACE preparations.

Amino Acid Sequence↗
PubMedDate not supplied

A statistical-based approach to assessing the fidelity of combinatorial libraries encoded with electrophoric molecular tags. Development and application of tag decode-assisted single bead LC/MS analysis.

A statistical sampling protocol is described to assess the fidelity of libraries encoded with molecular tags. The methodology, termed library QA, is based on the combined application of tag decode analysis and single bead LC/MS. The physical existence of library compounds eluted from beads is established by comparing the molecular weight predicted by tag decode with empirical measurement. The goal of sampling is to provide information on overall library fidelity and an indication of the performance of individual library synthons. The minimal sampling size n for library QA is l0 x the largest synthon set. Data are reported as proportion (p) +/- lower and upper boundary (lb-ub) computed at the 95% confidence level (alpha = 0.05). As a practical demonstration, library QA was performed on a 25,200-member library of statine amides (size = 40 x 63 x 10). Sampling was conducted three times at n approximately 630 beads per run for a total of 1902 beads. The overall proportions found for the three runs were consistent with one another: p = 84.4%, lb-ub = 81.5-87.2%; p = 83.1%, lb-ub = 80.2-85.95; and p = 84.5%, lb-ub = 81.8-87.3%, suggesting the true value of p is close to 84% compound confirmation. The performance pi of individual synthons was also computed. Corroboration of QA data with biological screening results obtained from assaying the library against cathepsin D and plasmepsin II is discussed.

Journal Article↗
PubMedDate not supplied

Antinociceptive properties of inhibitors of endopeptidase 24.15.

Endopeptidase 24.15, a metalloendopeptidase active in brain, rapidly converts prodynorphin-derived peptides into leu-enkephalin. Inhibitors of this enzyme slow the degradation of these peptides in vivo and in vitro. The present study evaluated two inhibitors of endopeptidase 24.15, N-[1-(RS)-carboxy-3-phenyl-propyl]-Ala-Ala-Phe-p-aminobenzoate (cFP-AAF-pAB), and N-[1-(RS)-carboxy-3-phenylpropyl]-Ala-D-Ala-Phe-p-aminobenzoate (cFP-A(D)AF-pAB), for antinociception on the tail-flick and jump tests in rats following intracerebroventricular administration relative to an inhibitor of endopeptidase 24.11, N-(1-(RS)-carboxy-3-phenylpropyl]-Phe-p-aminobenzoate (cFP-F-pAB). cFP-AAF-pAB, cFP-A(D)AF-pAB and cFP-F-pAB produced equipotent dose-dependent (25-250 nmol) and time-dependent (5-7 h) antinociception with larger effects on the jump (49-51% increase) relative to the tail-flick (28-41% increase) test. Naloxone (1 mg/kg, SC) significantly reduced antinociception elicited by all inhibitors on the jump test. Motor performance failed to be affected by inhibitor administration. The gradual appearance of antinociception and its naloxone sensitivity suggest that these effects are mediated through inhibition of opioid peptide degradation.

Animals↗
PubMedDate not supplied

Kidney as a site of uptake and metabolism of gamma-glutamyl compounds.

gamma-Glutamyl derivatives of amino acids are extensively metabolized and accumulated in the kidney. The kideny also has a high capacity to synthesize ophthalmic acid, an analog of glutathione. These processes can be attributed to the high activity in the kidney of enzymes that both degrade and synthesize glutathione. Th possibility of using the gamma-glutamyl group as a carrier for the introduction of compounds containing an amino function into kidney metabolism was explored. Administration of L-gamma-glutamyl-L-3,4-di-hydroxyphenylalanine (gamma-glutamyl-DOPA) to rats led to the accumulation of gamma-glutamyl-DOPA in the kidney, release of DOPA and its conversion to dopamine by the action of aromatic amino acid decarboxylase. Dopamine actively generated in the kidney increased renal plasma flow and sodium excretion. No systemic effects or untoward reactions attributable to this amine were observed. It is suggested that gamma-glutamyl derivatives of certain drugs may be useful as kidney specific prodrugs.

Amino Acids↗