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Biomedical subjects

E Shaw

Publications and source records attributed to E Shaw.

At least 109 records · Page 6Linked to original sources
PubMed1988

The synthesis and properties of peptidylmethylsulphonium salts with two cationic residues as potential inhibitors of prohormone processing.

Peptidylmethylsulphonium salts incorporating consecutive basic residues at the C-terminus of the peptidyl portion such as -Arg-Arg-, -Arg-Lys-, -Lys-Lys- and -Lys-Arg- were synthesized and examined as proteinase inhibitors. Serine proteinases with a specificity directed towards hydrolysis at cationic residues were found to be unaffected by these derivatives. On the other hand, cysteine proteinases, cathepsin B and, in particular, clostripain were readily inactivated by affinity labelling. The reagents thus are of promise for the study of prohormone processing promoted by cysteine proteinases.

Cathepsin B↗
PubMed1988

Synthesis and properties of peptidyl derivatives of arginylfluoromethanes.

Two peptide derivatives of arginylfluoromethane (Arg-CH2F), namely Bz(benzoyl)-Phe-ArgCH2F and D-Phe-Pro-Arg-CH2F, have been synthesized by extension of available methods, i.e. the Dakin-West reaction [Rasnick (1985) Anal. Biochem. 149, 461-465] or synthesis of a phthaloyl-blocked C-terminal fluoromethane [Rauber, Angliker, Walker & Shaw (1986) Biochem. J. 239, 633-640; Angliker, Wikström, Rauber & Shaw (1987) Biochem. J. 241, 871-875] with subsequent elongation. The guanidino group of arginine was protected as the bis-Cbz (benzyloxycarbonyl) derivative. The products were examined as active-site-directed inhibitors of some trypsin-related serine proteinases as well as a pair of cysteine proteinases. The results extend previous observations that the rate of alkylation of serine proteinases by fluoromethanes may be considerably slower than by chloromethanes. As expected, the amino acid sequence of the inhibitors influenced their relative effectiveness. Thus the rate of inactivation of a number of trypsin-like proteinases by D-Phe-Pro-Arg-CH2F varied by more than two orders of magnitude.

Hydrocarbons, Fluorinated↗
PubMed1988

The design of peptidyldiazomethane inhibitors to distinguish between the cysteine proteinases calpain II, cathepsin L and cathepsin B.

A series of peptidyldiazomethanes was synthesized and tested as inactivators of the cysteine proteinases calpain II, cathepsin L and cathepsin B. Inactivators that react rapidly and that show a degree of selectivity between the enzymes were identified. Z-Tyr(I)-Ala-CHN2 (where Z represents benzyloxycarbonyl) reacts rapidly with cathepsin L and more slowly with cathepsin B, but does not inhibit calpain II. Z-Leu-Leu-Tyr-CHN2 reacts rapidly with cathepsin L and calpain II but very slowly with cathepsin B. Boc-Val-Lys(epsilon-Z)Leu-Tyr-CHN2 (where Boc represents t-butyloxycarbonyl) reacts more rapidly with calpain II than with cathepsin L or cathepsin B. The discriminating inhibitory effects of these compounds make them potentially useful for investigation of enzyme functions in vivo. The data presented also provide insights into the subsite specificity of calpain.

Calpain↗
PubMed1988

Synthesis of lysine-containing sulphonium salts and their properties as proteinase inhibitors.

Some sulphonium salts derived from lysine were synthesized with the general structure R-Lys-CH2S+-(alkyl)2. They were examined as inhibitors of the cysteine proteinase clostripain, which has a preference for cleaving peptide bonds at the carboxy group of basic amino acids, and of a number of trypsin-related serine proteinases. Clostripain was irreversibly inactivated by all reagents examined, but in the case of the serine proteinases, depending on the reagent structure, irreversible and reversible inhibitions were observed. These were kinetically characterized.

Cysteine Endopeptidases↗
PubMed1988

Synthesis and properties of Cbz-Phe-Arg-CHN2 (benzyloxycarbonylphenylalanylarginyldiazomethane) as a proteinase inhibitor.

The preparation of peptides terminating in -Arg-CHN2 has been attempted because of their potential value as proteinase inactivators. We have succeeded in one case, converting Cbz-Phe-ArgOH to the diazomethane without blocking the guanidino group. As expected from previous results with such reagents, the new derivative was extremely effective in inactivating a cysteine proteinase specific for cleaving at arginyl bonds, that is, clostripain. However, in contrast with the inertness of serine proteinases to reagents of this type in the cases examined previously, plasma kallikrein was inactivated by Cbz-Phe-Arg-CHN2, although with a considerably lower rate constant than with clostripain. Trypsin, however, was not inactivated, but gradually destroyed the reagent, as had been observed previously with chymotrypsin and Cbz-Phe-CHN2. This has now been re-examined with rho-nitro-Cbz-Ala-Phe-CHN2 and shown to involve a cleavage to rho-nitro-Cbz-Ala-PheOH, probably with liberation of diazomethane.

Cathepsin B↗
PubMed1988

Peptidyl sulfonium salts. A new class of protease inhibitors.

The possibility has been examined that peptidylmethyl sulfonium salts might affinity label proteases by an alkyl transfer from sulfur to an active center residue. The synthesis of a number of agents of this type is described as well as initial results of their effect on cysteinyl proteases, papain and cathepsin B. These are readily inactivated by reagents in which the peptidyl portion contains features that promote binding to the proteases such as a penultimate phenylalanine residue. Irreversible inactivation ensues by transfer of the peptidyl portion, not methyl groups. Peptidylmethyl sulfonium salts lose a proton to form an ylide structure which may be the prevalent form at physiological pH values. The ylide may also be the active affinity labeling form of the reagent since the rate of inactivation of cathepsin B increases with pH. In contrast, the action of another affinity labeling reagent for cathepsin B, benzyloxycarbonyl-Phe-AlaCHN2, a diazomethyl ketone, is relatively independent of pH.

Affinity Labels↗
PubMed1988

Active center differences between cathepsins L and B: the S1 binding region.

The substrate peptide bond cleaved by cathepsins B and L is determined not by the amino acid contributing the carboxyl group to this bond as in the case of serine proteases but rather by the presence of a neighboring amino acid with a large hydrophobic side chain. From a study of the inhibitory potency in a series, Cbz-Phe-X-CHN2, in which Phe promotes binding at S2 (terminology of [(1968) Biochem. Biophys. Res. Commun. 32, 898-902]) while the amino acid X probes S1, it is shown that this region of cathepsin L also has the ability to accommodate large hydrophobic side chains. In this respect cathepsin L differs from cathepsin B. Thus Cbz-Phe-Tyr(O-t-Bu)CHN2 inactivates cathepsin L with a rate 2.5 x 10(4) greater than that for cathepsin B.

Amino Acids↗
PubMed1988

Iodination of peptidyl chloromethyl ketones for protease affinity labels.

The specificity of peptidyl chloromethyl ketones has been used to label proteases in complex biological systems by incorporating tyrosine into the structure for eventual radioiodination. Contrary to results with iodination of proteins, a mild reagent, that is, one which iodinates at neutrality, was unsuitable, giving complex mixtures with poor reproducibility, apparently because of side reactions at the chloromethyl ketone group. On the other hand, iodine monochloride in acetic acid provided clean products. In the cases examined where a tyrosine residue was not appropriate for the specificity of the target protease, this residue was located well displaced from the primary specificity site. The resultant diiodotyrosine-containing derivatives were generally highly active as protease inhibitors. The p-aminobenzoyl group was used as an alternative to tyrosine as an iodinatable component.

Affinity Labels↗
PubMed1988

Borreliosis in equids in northeastern United States.

During 1982 and 1985, blood samples from 705 equids were examined for antibodies to Borrelia burgdorferi. By indirect immunofluorescence staining, IgM and total immunoglobulin (IgM and IgG) antibodies were detected in 37 (5.3%) and 90 (12.8%) serum specimens, respectively. The geometric mean titer for IgM antibody (140.4) was highest during July, whereas total immunoglobulin ranged from 94.1 in October to 338 in May. Eighty-six equids with total immunoglobulin to B burgdorferi lived in areas of Connecticut where the primary tick vector, Ixodes dammini, was present. Of the 86 equids, 9 from Lyme, Connecticut and Westchester County, New York had antibodies to B burgdorferi and developed limb or joint disorders that resulted in single or recurrent episodes of lameness.

Animals↗
PubMed1987

The synthesis of lysylfluoromethanes and their properties as inhibitors of trypsin, plasmin and cathepsin B.

The synthesis of two lysylfluoromethanes is described by an extension of the synthesis method of Rauber, Angliker, Walker & Shaw [(1986) Biochem. J. 239, 633-640]. Ala-Phe-Lys-CH2F was found to be an active-centre-directed inhibitor of plasmin and trypsin, as is the corresponding chloromethane. However, the rate of covalent-bond formation is about an order of magnitude lower at 25 degrees C for the fluoro derivative. It was, in addition, an extremely effective inactivator of cathepsin B at pH 5.4 and 6.4. The chemical reactivity of fluoromethanes was compared with that of chloromethanes as alkylators of GSH. At pH 7.4 and 37 degrees C, a fluoromethane has 1/500th the reactivity of a chloromethane. A comparison of the rates of reaction of the fluoromethane with cathepsin B and with GSH at pH 6.4 revealed an enhancement of 10(8)-fold for the alkylation of the enzyme, ascribable largely to a proximity effect.

Alkylation↗
PubMed1987

Improved synthetic inactivators of plasmin.

Synthetic inhibitors for plasmin of the peptidyl chloromethyl ketone type are described which have increased effectiveness due to side-chains which improve affinity to auxiliary binding regions of the active center.

Amino Acid Chloromethyl Ketones↗
PubMed1986

The synthesis of peptidylfluoromethanes and their properties as inhibitors of serine proteinases and cysteine proteinases.

A synthesis of peptidylfluoromethanes is described that utilizes the conversion of phthaloyl amino acids into their fluoromethane derivatives. These can be deblocked and elongated. The inactivation of chymotrypsin by Cbz-Phe-CH2F (benzyloxycarbonylphenylalanylfluoromethane) was found to be considerably slower than that of the analogous chloromethane. The fluoromethane analogue inactivates chymotrypsin with an overall rate constant that is 2% of that observed for the inactivation of the enzyme with the chloromethane. However, the result is the same. The reagent complexes in a substrate-like manner, with Ki = 1.4 X 10(-4) M, and alkylates the active-centre histidine residue. Cbz-Phe-Phe-CH2F and Cbz-Phe-Ala-CH2F were investigated as inactivators of the cysteine proteinase cathepsin B. The difference in reactivity between fluoromethyl ketones and chloromethyl ketones is less pronounced in the case of the cysteine proteinase than for the serine proteinase. Covalent bond formation takes place in this case also, as demonstrated by the use of a radiolabelled reagent.

Cathepsin B↗
PubMed1986

Heterogeneity in late-onset metachromatic leukodystrophy. Effect of inhibitors of cysteine proteinases.

The synthesis of arylsulfatase A polypeptides was followed in fibroblasts from 11 patients with late-onset forms of metachromatic leukodystrophy. In 10 cell lines, the apparent rate of synthesis was 20%-70% as measured by the amount of [35S]arylsulfatase A secreted in the presence of 10 mM NH4Cl. The specific activity of the secreted arylsulfatase A was normal. The residual activity of arylsulfatase A was below 10% except for one cell line in which it was 20%. The activity of arylsulfatase A and the degradation of sulfatides was partially restored in these fibroblast lines by treatment with irreversible (peptidyl diazomethyl ketones) or competitive (leupeptin) inhibitors of cysteine proteinases. Thus, the mutation(s) in these cell lines led to the synthesis of arylsulfatase. A polypeptides with increased susceptibility to cysteine proteinases. Multiple allelic mutations within this group of late-onset metachromatic leukodystrophy were suggested by the clinical heterogeneity, the variability of the residual activity, and in the response to inhibitors of cysteine proteinases. In fibroblasts from one patient, the apparent rate of synthesis of arylsulfatase A was less than 5%. Furthermore, inhibitors of cysteine proteinases were without effect, suggesting that the mutation in this patient is different from the others.

Adolescent↗
PubMed1986

Peptidyl fluoromethyl ketones as thiol protease inhibitors.

The fluoromethyl ketone derivatives of peptides are now available through several synthetic approaches and can be examined with respect to their properties as protease inhibitors. It had been expected that the fluoro atom might be too inert for nucleophilic displacement and that irreversible inactivation might not be achievable by this type of derivative in contrast to chloromethyl ketones. However, with serine and cysteinyl proteases, alkylation of the enzyme does take place although the rates are not similar to those of the chloromethyl ketones. Of the two classes, thiol proteases are more readily inactivated and the fluoromethyl ketones are almost as effective as the chloromethyl ketones. Our observations confirm and extend those of Rasnick (Anal. Biochem. 149, 461-465 (1985)). The structure of the peptidyl portion of the reagent controls specificity of inhibition in the typical manner of affinity-labels for proteases. However, fluoromethyl ketones are considerably less reactive to nucleophiles such as the thiol group of glutathione, than chloromethyl ketones and, therefore, this new class of inhibitors may provoke fewer side reactions when used in biological studies.

Amino Acids↗