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We screened a series of new epoxysuccinyl peptides for the development of a lysosomal cathepsin L-specific inhibitor. Among the compounds tested, (2S,3S)-oxirane-2,3-dicarboxylic acid 2-[((S)-1-benzylcarbamoyl-2-phenyl-ethyl)-amide] 3-{[2-(4-hydroxy-phenyl)-ethyl]-amide} (compound CAA0225) was the most potent inhibitor of cathepsin L. CAA0225 inhibited rat liver cathepsin L with IC50 values of 1.9 nM, but not rat liver cathepsin B (IC50, >1000-5000 nM). To assess the contribution of cathepsin L to lysosomal proteolysis, we evaluated autophagy, which is the process of lysosomal self-degradation of cell constituents. In HeLa and Huh-7 cells cultured under nutrient-deprived conditions CAA0225 significantly inhibited degradation of long-lived proteins; however, the magnitude of inhibition was comparable to that in the presence of CA-074-OMe, which is a cathepsin B-specific inhibitor. Thus the contributions of cathepsin L and cathepsin B to autophagic protein degradation of cytoplasmic proteins are nearly equal. During autophagy, microtubule-associated protein IA/IB light chain 3-II (LC3-II) and gamma-aminobutyric acid (A) receptor-associated protein (GABARAP)-II, which are specific markers of autophagosomal membranes that engulf cytoplasmic components, also undergo degradation upon fusion of autophagosomes with lysosomes. CAA0225 effectively inhibited degradation of LC3-II and GABARAP, whereas CA-074-OMe had only a marginal effect on their levels. Therefore we conclude that cathepsin L does not play a general role in the degradation of proteins in the lumen of autophagosomes, but rather is involved specifically in the degradation of autophagosomal membrane markers.

Glucose incorporation is regulated mainly by GLUT4 in skeletal muscles. Here we report that treatment of L6 myotubes with scriptide, a hydroxamic acid-based histone deacetylase (HDAC) inhibitor, stimulated 2-deoxyglucose uptake. The effect appeared only after 24 hr, resulting in 2.4-fold glucose uptake at treatment day 6. Scriptide acted synergistically with insulin, indicating it stimulated a distinct pathway from the insulin signaling pathway. It was not observed in undifferentiated myoblasts or 3T3-L1 adipocytes, suggesting a muscle-specific effect of scriptide. A five-carbon chain and hydroxamic acid, essential for histone deacetylase inhibition, were indispensable for this effect, and trichostatin A stimulated glucose uptake as well. Scriptide increased the cellular content of GLUT4, and induced GLUT4 translocation, but GLUT4 mRNA level did not change, indicating scriptide functions posttranslationally. Our results indicated a novel function for HDAC inhibitors of increasing GLUT4 content and its translocation in muscle cells, resulting in stimulation of glucose uptake.

In order to elucidate the substrate specificity of the Sn subsites (n=1-3) of cathepsin B, its crystal structure inhibited by E64c [(+)-(2S,3S)-3-(1-[N-(3-methylbutyl)amino]-leucylcarbonyl)oxirane-2-carboxylic acid] was analyzed by the X-ray diffraction method. Iterative manual rebuilding and convenient conjugate refinement of structure decreased R- and free R-factors to 19.7% and to 23.9%, respectively, where 130 water molecules were included for the refinement using 14,759 independent reflections from 10 to 2.3 A resolution. The epoxy carbonyl carbon of E64c was covalently bonded to the Cys(29) S(gamma) atom and the remaining parts were located at Sn subsites (n=1-3). The substrate specificity of these subsites was characterized based on their interactions with the inhibitor. Base on these structural data, we developed a novel cathepsin B-specific noncovalent-type inhibitor, which may bind to S2'-S3. The molecular design of possessing structural elements of both CA074 and E64c, assisted by energy minimization and molecular dynamics (MD) simulation, may lead to a new lead noncovalent-type inhibitor.

The Ile-Pro sequence of CA074, potent covalent-type inhibitor, is necessary to exhibit the specificity for cathepsin B, but not for papain. In order to elucidate how its sequence binds to papain and why such binding does not exhibit the specificity for papain at the atomic level, two CA074-related compounds, 1 (N-(L-3-carboxyloxirane-2-carbonyl)-L-isoleucyl-L-proline) and 2 (N-(L-3-carboxyloxirane-2-carbonyl)-L-isoleucyl-diethylamide), were designed and their structure--inhibitory activity relationship was investigated by the X-ray crystal analyses of the complexes with papain. The Ile-Pro moiety of 1 was located at the S2 and S3 subsites consisting of Val-133, Val-157, and Asp-158 and of Tyr-61, Gly-66, and Tyr-67 residues of papain, respectively, which is in contrast with the binding of CA074 to S'n (n = 1 approximately 2) subsites in the complex with cathepsin B. Although 2 in the complex with papain showed the similar binding pattern to 1, its inhibitory activity was about two-fold higher than of 1, suggesting the importance of tight S3-P3 hydrophobic interaction for the activity. The difference of the substrate specificity between papain and cathepsin B has also been discussed based on the X-ray results of the present and cathepsin B-inhibitor complexes.

The binding mode of CA074 [N-(L-3-trans-propylcarbamoyl-oxirane-2-carbonyl)-L-isoleucyl-L-pr oline], a specific irreversible inhibitor, to bovine spleen cathepsin B was elucidated by X-ray crystal structure analysis of the complex at 2.2 A resolution (conventional R=0.185). Inconsistently with our model used for the development of CA074, the L-isoleucyl-L-proline and propylcarbamoyl moieties are located at the S' and S subsites, respectively. This unexpected binding is primarily due to (i) similar extended chain conformations (due to the same S configurations) at the oxirane C2 and C3 atoms of CA074 and (ii) the just fit formation of double hydrogen bonds between the carboxyl oxygens of L-proline and the imidazole nitrogens of His-110 and His-111 residues (these residues are missing in papain, the tertiary structure of which was used for the design of CA074). The oxirane C3 atom possessing the P' substituent is covalently bound to the Cys-29 Sgamma atom (C3-Sgamma=1.79 A) and the S configuration is maintained. The present result will provide useful information for characterizing the substrate-specificity of cathepsin B.

The absorption, distribution and excretion of 14C-tulobuterol following daily dermal application at 10 mg/kg for 7 days was examined in rats. 1. Blood radioactivity reached a steady state after the 4th dose. After the final dose, blood radioactivity showed maximum values of 506.1 ng eq./ml at 5 hr and disappeared with T1/2 of 19.4 hr as also noted for T1/2 after a single application (15.7 hr). 2. After the final application, the radioactivity in most tissues was higher than after a single application. Elimination of radioactivity in tissue was basically the same as after a single application. 3. Within 168 hr after the 7th application, urinary and fecal excretion was 53.8 and 36.3% of the dose, respectively. Recovery in urine and feces and from residue in the removed tape was 98.6% of the dose.

The absorption, distribution and excretion of 14C-tulobuterol or unlabeled tulobuterol following a single application was examined in infant rats. 1. After a single dermal application of a tape containing 14C-tulobuterol at 10 mg/kg, blood radioactivity reached maximum at 4 hr in male and female infant rats, respectively. Radioactivity disappeared with T1/2 of 17.0 and 17.3 hr in male and female infant rats, respectively. 2. After a single dermal application of unlabeled tulobuter ol at 5, 10 and 20 mg/kg to male infant rats, blood levels of unchanged tulobuterol reached maximum at 4.0 hr and then disappeared with T1/2 of 2.8-2.9 hr. Cmax and AUC increased dose-dependently within a dose range of 5-20 mg/kg. 3. After a single dermal application of 14C-tulobuterol to male infant rats, the radioactivity in nearly all tissues reached maximum at 4 hr. Radioactivity was distributed well in target organs such as the lung and trachea, and was particularly high in the skin at the site of application followed by the liver and kidney. 4. After a single dermal application of 14C-tulobuterol at 10 mg/kg, the urinary and fecal excretion of radioactivity within 168 hr was 50.1 and 30.5% in male infant rats and, 52.5 and 32.2% in female infant rats, respectively. Recoveries in urine and feces and from residue in the removed tape was almost complete in male (99.4%) and female (98.5%) rats.

The absorption, distribution, metabolism and excretion of 14C-tulobuterol or unlabeled tulobuterol following a single dermal application was examined in rats. 1. After a single dermal application of a tape containing 14C-tulobuter ol at 10 mg/kg, blood radioactivity reached maximum at 2 and 4 hr in male and female rats, respectively. Radioactivity decreased with T2 of 15.9 and 15.7 hr in male and female rats, respectively. 2. After a single dermal application of unlabeled tulobuterol at 5, 10 and 20 mg/kg to male rats, blood levels of unchanged tulobuterol reached maximum at 4.0-5.5 hr and then disappeared with T2 of 2.6-2.9 hr.The bioavailability of tulobuterol was about ten times that after an oral administration. Cmax and AUC increased in dose-dependent manner within a dose range of 5-20 mg/kg. 3. After a single dermal application of 14C-tulobuterol to male rats, radioactivity in nearly all tissues reached maximum at 4 hr. The radioactivity was distributed well in target organs such as lung and trachea, and was particularly high in the skin at the site of application followed by liver and kidney. 4. Metabolites in urine after a subcutaneous dose of tulobuterol were essentially the same as after an oral administration. The unchanged tulobuterol increased from 0.1 to 3.1% of the dose when the route of administration was changed from oral to subcutaneous. 5. After a single dermal applic ation of 14C-tulobuterol at 10 mg/kg, urinary and fecal excretions of radioactivity within 168 hr were 50.8 and 35.4% in male rats and, 52.8 and 34.7% in female rats, respectively. Recovery in urine and feces and from residue in the tape was almost complete in the male (99.5%) and female (100.3%) rats.

In order to investigate the stereo specificity of papain Sn subsites (n = 1-4) at the atomic level, two kinds of covalent-type inhibitors were designed based on the previous results on papain-E-64 and papain-E-64-c interactions, and their complex crystals with papain were analyzed by X-ray diffraction. The results show that the hydrophobic regions consisting of Val-133, Val-157 and Asp-158 and of Tyr-61, Gly-66 and Tyr-67 residues interact with the hydrophobic P2 and P3 side chains of inhibitors, thus indicating the function of the former and latter binding pockets as S2 and S3 subsites, respectively. Furthermore, the X-ray analysis suggests that the papain has no definite Sn subsite of nor = 4, and the S3-P3 hydrophobic interaction is significantly affected by the Pn side chain (nor = 4) of both the substrate and the inhibitor.

Inactivators of cysteine proteinases (CPs) were tested as inhibitors of bone resorption in vitro and in vivo. The following four CP inactivators were tested: Ep475, a compound with low membrane permeability which inhibits cathepsins B, L, S, H, and calpain; Ep453, the membrane-permeant prodrug of Ep475; CA074, a compound with low membrane permeability which selectively inactivates cathepsin B; and CA074Me, the membrane-permeant prodrug of CA074. The test systems consisted of 1) monitoring the release of radioisotope from prelabelled mouse calvarial explants and 2) assessing the extent of bone resorption in an isolated osteoclast assay using confocal laser microscopy. Ep453, Ep475, and CA074Me inhibited both stimulated and basal bone resorption in vitro while CA074 was without effect; the inhibition was reversible and dose dependent. None of the inhibitors affected protein synthesis, DNA synthesis, the PTH-enhanced secretion of beta-glucuronidase, and N-acetyl-beta-glucosaminidase, or the spontaneous release of lactate dehydrogenase. Ep453, Ep475, and CA074Me dose-dependently inhibited the resorptive activity of isolated rat osteoclasts cultured on bone slices with a maximal effect at 50 microM. The number of resorption pits and their mean volume was reduced, whilst the mean surface area remained unaffected. Again, CA074 was without effect. Ep453, Ep475, and CA074Me, but not CA074, when administered subcutaneously at a dose of 60 micrograms/g body weight inhibited bone resorption in vivo as measured by an in vivo/in vitro assay, by about 20%. This study demonstrates that cathepsins B, L, and/or S are involved in bone resorption in vitro and in vivo. Whilst cathepsin L and/or S act extracellularly, and possibly intracellularly, cathepsin B mediates its effects intracellularly perhaps through the activation of other proteinases involved in subosteoclastic collagen degradation.

OBJECTIVE To investigate mechanisms of cartilage matrix destruction by a study of the effects of a specific inactivator of cathepsin B and an inhibitor of several matrix metalloproteinases (MMP) on cartilage proteoglycan release. METHODS Cartilage explants were treated with either recombinant human interleukin-1 alpha (rHuIL-1 alpha) or retinoic acid in the presence or absence of the inhibitors, and proteoglycan release was quantitated. Tests for nonspecific effects of the inhibitors included reversibility, rates of protein synthesis and glycolysis, and effects on other rHuIL-1 alpha-mediated events. RESULTS The cathepsin B inactivator inhibited rHuIL-1 alpha-stimulated proteoglycan release at nanomolar concentrations, but failed to significantly inhibit retinoic acid-stimulated proteoglycan release. An inhibitor of MMP was inhibitory to both rHuIL-1 alpha-stimulated release and retinoic acid-stimulated release. CONCLUSION Cathepsin B is implicated in rHuIL-1 alpha-stimulated loss of cartilage proteoglycan. Its lack of involvement in retinoic acid-stimulated proteoglycan release suggests the existence of at least 2 pathways of cartilage proteoglycan breakdown, which may converge at the activation of a matrix prometalloproteinase.

The specificity of compound CA074 [N-( l -3-trans-propylcarbamoyloxirane-2-carbonyl)- l -isoleucyl- l -proline] for the inactivation of cathepsin B was quantified in in vitro measurements with cysteine endopeptidases from cattle, it being found that the compound is a very rapid inactivator of cathepsin B (rate constant 112,000 m −1 · s−1), with barely detectable action on cathepsins H, L, and S or m-calpain. Conversion of the proline carboxyl group of the inhibitor to the methyl ester virtually abolished the effect on cathepsin B, and a possible explanation for the importance of the carboxyl is presented on the basis of the tertiary structure of cathepsin B. It was found that CA074 methyl ester (1 μ m , 3 h) caused selective inactivation of the intracellular cathepsin B of human gingival fibroblasts in culture, in contrast to other available agents, and we suggest that CA074 methyl ester will be of value in the elucidation of the biological functions of cathepsin B.

To design a potent inhibitor specific for cathepsin B (rat liver), the tertiary structure was predicted based on the crystal structure of the papain complexed with (+)-(2S,3S)-3-(1-[N-(3-methylbutyl)amino]leucylcarbonyl)oxirane-2- carbolylic acid (E-64-c), a thiol protease inhibitor. Taking advantage of the structural characteristics of the predicted active site, seventeen inhibitors were chemically synthesized by molecular modeling, and one of them, N-(L-3-trans-propylcarbamoyloxirane-2-carbonyl)-L-isoleucyl-L-p rol ine (CA-074) was shown to be the first potent inhibitor specific for cathepsin B. The relationship between the structure and inhibitory activity is discussed based on the model structure of the cathepsin B-inhibitor complex.

New derivatives of E-64 (compound CA-030 and CA-074) were tested in vitro and in vivo for selective inhibition of cathepsin B. They exhibited 10000–30000 times greater inhibitory effects on purified rat cathepsin B than on cathepsin H and L; their initial K1 values for cathepsin B were about 2–5 nM, like that of E-64-c, whereas their initial K1 values for cathepsins H and L were about 40–200 μM. In in vivo conditions, such us intraperitoneal injection of compound CA-030 or CA-074 into rats, compound CA-074 is an especially potent selective inhibitor of cathepsin B, whereas compound CA-030 does not show selectivity for cathepsin B, although both compounds CA-030 and CA-074 show complete selectivity for cathepsin B in vitro.

A series of new epoxysuccinyl peptides were designed and synthesized to develop a specific inhibitor of cathepsin B. Of these compounds, N-(L-3-trans-ethoxycarbonyloxirane-2-carbonyl)-L-isoleucyl-L-proline (compound CA-030) and N-(L-3-trans-propylcarbamoyloxirane-2-carbonyl)-L-isoleucyl-L-proline (compound CA-074) were the most potent and specific inhibitors of cathepsin B in vitro. The carboxyl group of proline and the ethyl ester group or n-propylamide group in the oxirane ring were necessary, the ethyl ester group or the n-propylamide group being particularly effective for distinguishing cathepsin B from other cysteine proteinases such as cathepsins L and H, and calpains.

1. The urinary and plasma metabolites of 14C-loxistatin, a new thiol protease inhibitor, were studied after oral administration to rats. 2. The major metabolites in urine were identified as loxistatin acid (M-1), a pharmacologically active form, and its hydroxy metabolites (M-4a and M-4b). These metabolites were also shown to be the major metabolites in plasma. 3. The inhibitory activity of the synthetic metabolite, M-4b, on papain was almost the same as that of loxistatin acid.

To quantitatively estimate the inhibitory effect of each substrate-binding subsite of cathepsin B (CB), a series of epoxysuccinyl derivatives with different functional groups bound to both carbon atoms of the epoxy ring were synthesized, and the relationship between their inhibitory activities and binding modes at CB subsites was evaluated by the X-ray crystal structure analyses of eight complexes. With the common reaction in which the epoxy ring of inhibitor was opened to form a covalent bond with the SgammaH group of the active center Cys29, the observed binding modes of the substituents of inhibitors at the binding subsites of CB enabled the quantitative assessment of the inhibitory effect of each subsite. Although the single blockage of S1' or S2' subsite exerts only the inhibitory effect of IC50 = approximately 24 microM (k2 = approximately 1250 M(-1) s(-1)) or approximately 15 microM (k2 = approximately 1800 M(-1) s(-1)), respectively, the synchronous block of both subsites leads to IC50 = approximately 23 nM (k2 = 153,000 - 185,000 M(-1) s(-1)), under the condition that (i) the inhibitor possesses a P1' hydrophobic residue such as Ile and a P2' hydrophobic residue such as Ala, Ile or Pro, and (ii) the C-terminal carboxyl group of a P2' residue is able to form paired hydrogen bonds with the imidazole NH of His110 and the imidazole N of His111 of CB. The inhibitor of a Pn' > or = 3' substituent was not potentiated by collision with the occluding loop. On the other hand, it was suggested that the inhibitory effects of Sn subsites are independent of those of Sn' subsites, and the simultaneous blockage of the funnel-like arrangement of S2 and S3 subsites leads to the inhibition of IC50 = approximately 40 nM (k2 = approximately 66,600 M(-1) s(-1)) regardless of the lack of Pn' substituents. Here we present a systematic X-ray structure-based evaluation of structure-inhibitory activity relationship of each binding subsite of CB, and the results provide the structural basis for designing a more potent CB-specific inhibitor.

The in vivo activity of olamufloxacin (HSR-903), a new fluoroquinolone, was evaluated and compared with ciprofloxacin, sparfloxacin and levofloxacin. Olamufloxacin was active against systemic infection in mice inoculated with both Gram-positive and -negative bacteria. Olamufloxacin had equal efficacy for experimental urinary tract infections in mice caused by Pseudomonas aeruginosa.

The crystal structure of the bovine spleen cathepsin B (BSCB)-CA074 complex was refined to R = 0.152 using X-ray diffraction data up to 2.18 A resolution. BSCB is characterized by an extra Cys148-Cys252 disulfide bridge, as compared with rat and human CBs. Although the crystal structures of these enzymes showed similar overall folding, a difference was observed in the occluding loop, a structural element specific only to CB. Comparison of the torsion angles indicated the different flexibilities of their loop structures. The oxirane C6 atom of CA074 was covalently bonded to the Cys29 S(gamma) atom (C3-S(gamma)=1.81 A), where the S-configuration was transformed to the R-form. Concerning the oxirane carbon atom that participates in the covalent bonding with the Cys residue, an acceptable rule has been proposed. The substrate specificities at the Sn (n = 1-3) and Sn' (n=1 and 2) subsites of CB, together with the interaction features as to CA074, have been discussed in comparison with the crystal structure of the papain-CA028 (a CA074-related inhibitor) complex.

Cathepsin B from bovine spleen has been purified and crystallized as a complex with a specific inhibitor CA074 [N-(L-3-trans-propylcarbamoyloxirane-2-carbonyl)-L- isoleucyl-L-proline], using the hanging-drop method. The complex crystals obtained from 50 mM-citrate buffer (pH 3.5) belong to the tetragonal space group P4(1) (or P4(3)) with a = 73.06 A and c = 141.59 A, and diffract beyond 2.2 A resolution. There are two complex molecules per asymmetric unit giving a packing density of 3.37 A3/Da and indicating a high solvent content of 63.5%.

The synthesis, antibacterial activity and oral absorption in rats of new 7 beta-[(Z)-2-(2-aminothiazol-4-yl)-2-(carboxymethoxyimino)ace tamido] cephalosporins (1) having various substituted-alkylthio groups at the C-3 position of the cephem nucleus are described. Of these, the cephalosporins with a cyanomethylthio group (1d) and fluoroethylthio group (1p) at the C-3 position showed a potent in vitro antibacterial activity against Gram-positive and Gram-negative bacteria as well as good oral absorption in rats. When administered orally to mice infected with Klebsiella pneumoniae, 1d had stronger protective effect than 1p. The structure-activity relationships of 1 are also presented.

Publisher Summary This chapter concerns specifically the algorithm of Needleman and Wunsch and its extension to a practical three-way comparison method. The use of a gap penalty weighted for the residues involved in the secondary structure of one of the proteins seems to improve the quality of alignments. The problem here, of course, is that accurate information on the secondary structure is not always available. When such information is available, however, the use of this method is recommended, as it is easily implemented in computer programs. The Needleman–Wunsch algorithm for the comparison of more than two sequences requires a large amount of computer memory. The same algorithm can be employed for the comparison of longer sequences by carrying out the matrix calculations for a limited number of cells in L. A shortcut method similar to the one described by Kruskal and Sankoff can be used. The use of a gap penalty weighted for the residues involved in the secondary structure of one of the proteins seems to improve the quality of alignments. The problem here, of course, is that accurate information on the secondary structure is not always available.

The synthesis, antibacterial activity and oral absorption of new 7 beta-[D-alpha-amino-alpha-(4-hydroxyphenyl)acetamido]cephalosporins (1) with various O-substituents at the C-3 position of a cephalosporin nucleus are described. Of these, the cephalosporins (1b-1e) having an alkoxycarbonylmethoxy group at the C-3 position showed good oral absorption in rats as well as potent activity against Gram-positive bacteria. The structure-activity relationships of 1 are also presented.

Ethly (+)-(2S, 3S) -3- [(S) -3-methyl-1- (3-methylbutylcarbamoyl) butylcarbamoyl] -2- oxirane-carboxylate (EST ; la) is expected to be useful as an oral therapeutic agent for muscular dystrophy on the basis of its potent inhibitory activities against the cysteine proteinases involved in the myofibrillar protein degradation that occurs in the disease. Through extensive investigations aimed at developing a new synthetic method for la that would be suitable for industrial application, it has been found that L-arginine can be used as a new, efficient resolving agent to obtain optically pure L-trans-epoxysuccinic acid (3a), and the active ester method using p-nitrophenol is very effective in the coupling reaction of ethyl L-trans-epoxysuccinate (7a) and L-leucine isoamylamide (8a) because of the extremely low formation of by-products.To examine the contribution of the stereochemistry of the trans-epoxysuccinic acid and leucine moieties to the inhibitory activity against cysteine proteinases, the diastereomers (lb-d) of la were synthesized by a similar method and the rate constants of inactivation of papain by la-d were measured. Compound la, having L-trans-epoxysuccinic acid and L-leucine moieties, showed the most potent activity among them.

The complete amino acid sequence of the plastocyanin from the green alga Enteromorpha prolifera has been determined by Edman degradation of the intact molecule and fragments produced by enzymatic cleavage of the polypeptide chain with chymotrypsin, Staphylococcus aureus protease, proline-specific endopeptidase, Lys-C endopeptidase and trypsin. The molecule consists of 98 amino acid residues with a calculated relative molecular mass of 10103. The amino acid sequence of E. prolifera plastocyanin shows a high degree of homology with those plastocyanins from other algae and higher plants. In particular, the four residues which are copper ligands in other plastocyanins and in the bacterial electron transport protein azurin (two histidines, one cysteine and one methionine) are conserved. Five out of the six acidic amino acid side-chains which create an 'acidic patch' on the surface of plastocyanin from Populus nigra var. italica [Colman, P. M. et al. (1978) Nature (Lond.) 272, 319-324] are conserved in the amino acid sequence of E. prolifera plastocyanin.

Syntheses a partir de phenol-6 6H-isoselenazolo- ou -isothiazolo [4,3-d] pyrimidones-7 ou de dimethyl-4,6 tetrahydro-4,5,6,7 isoselenazolo- ou -isothiazolo [4,3-d] pyrimidinediones-5,7 via l'acylation par des bromures d'α-bromoalcanoyle d'amides d'acides amino-4 isoselenazole- ou -isothiazolecarboxyliques-3

The three-dimensional structure of plastocyanin, a ‘blue’ or ‘Type 1’ copper-protein, has been determined at a resolution of 2.7 A. The copper atom has a highly distorted tetrahedral coordination geometry. It is coordinated by a cysteine thiol group, a methionine thioether group, and two histidine imidazole groups.

The synthesis, antibacterial activity and oral absorption in rats of 3-alkoxycarbonyl-methoxy-7 beta-[(Z)-2-(2-aminothiazol-4-yl)-2-(O-substituted oxyimino)acetamido]cephalosporins (1) are described. In this cephalosporin series, 7 beta-[(Z)-2-(2-aminothiazol-4-yl)-2-(carboxy-methoxyimino)acetamid o] cephalosporins (1b, 1i and 1j) with a lower alkoxycarbonylmethoxy group at the C-3 position of a cephem nucleus exhibited not only potent activity against Gram-negative bacteria but also good oral absorption in rats. Structure-activity relationships of 1 are also presented.

Three normal and branched alkane mixtures: n-pentane+n-hexane+n-heptane, 2-methylbutane+2-methylpentane+2-methylhexane, and 2-methylbutane+n-pentane+2-methylpentane+n-hexane+2-methylhexane+n-heptane were pyrolyzed at 700°C under atmospheric pressure. The alkane mixtures were diluted by nitrogen so as to give almost the same partial pressure for each component as that in the commercial cracking of naphtha, and the product distributions over a wide range of conversions are presented. A simulation model for the product distribution, which has been proposed for pure alkane in a previous study, was applied to the pyrolysis of alkane mixtures by taking into account the interaction between coexisting components. It was found by comparing with the experimental results that the present simulation model can be applied to simulate the product distributions over a wide range of conversions for normal and branched alkane mixtures.

X-ray absorption spectra for copper(II) plastocyanin have been measured at low temperature. These data confirm our previous observation (based on room-temperature measurements) that the methionine sulfur in plastocyanin makes no significant contribution to the Cu EXAFS and that the Cu-S(Met) interaction must therefore be extremely weak. Both preliminary data, having a very poor signal/noise ratio and subsequent measurements with much higher quality data are reported. Analysis of the preliminary data provides a cautionary example of the dangers of deriving structural results from noisy EXAFS data, at least in cases where the scatter is weakly contributing to the signal. Analysis of the near-edge structure gives direct evidence for x-ray-induced photoreduction of Cu(II) when extremely intense x-rays from synchrotron sources are used. The rate of photoreduction decreases by approximately a factor of 2 between 190 and 4 K, but it is still significant even at the lower temperatures studied. 38 refs., 7 figs., 3 tabs.

Lysosomal beta-galactosidase precursor is processed to a mature form and associated with protective protein in lysosomes. In this study we used two cysteine protease proinhibitors, E64-d for cathepsins B, S, H, and L, and CA074Me for cathepsin B. They are converted intracellularly to active forms, E-64c and CA074, respectively. Both active compounds inhibited maturation of the exogenous beta-galactosidase precursor, but E-64c did not inhibit further degradation to an inactive 50-kDa product. We concluded that cathepsin B participated exclusively in maturation of beta-galactosidase, and a non-cysteine protease was involved in further degradation and inactivation of the enzyme molecule.

The plastocyanins from a green alga (Enteromorpha prolifera) and cucumber (Cucumis sativus) have been crystallized. Crystal data are as follows: E. prolifera plastocyanin, space group I4, a = b = 53.9 A, c = 59.4 A, Z = 8; C. sativus plastocyanin, space group P4(1) (or P4(3) ), a = b = 66.7 A, c = 46.0 A, Z = 8. Accordingly, the asymmetric units of the crystals contain one and two molecules, respectively.

As a basic study on the efficient synthesis of chromogenic and fluorogenic peptidase substrates, we investigated possible general methods for the synthesis of α-amino acid and peptide amides of aromatic amines. Preparation of Boc-L-Leu-pNA (1) as a model compound was attempted by (1) the coupling of Boc-L-Leu-OH with p-nitroaniline, (2) the reaction of Boc-L-Leu OH with p-nitrophenyl isocyanate, and (3) the reaction of Boc-L-Leu-OH with the product formed from p-nitrobenzoic acid through the modified Curtius reaction with diphenyl phosphorazidate ((C6H5O) 2P (O) N3) in a one-pot process. The third method was found to be a general and efficient method for the preparation of α-amino acid amides of aromatic amines. Application of this method to the preparation of a peptidase substrate, Bz-L-Ile-L-Glu (OMe) -Gly-L-Arg-pNA (2), has also been successfully achieved.

A hemoglobin polymorphism involving variant beta-chains was demonstrated in the Celebes black ape, Macaca nigra. Fingerprinting and amino acid analysis of the tryptic peptides from the two chain types have shown that they differ by a single amino acid substitution, between lysine and aspartic acid, which requires a two-nucleotide change in the corresponding codon. Another substitution in the same codon is found as a species between the black ape and that of other macaques.

Ethly (+)-(2S, 3S) -3- [(S) -3-methyl-1- (3-methylbutylcarbamoyl) butylcarbamoyl] -2- oxirane-carboxylate (EST ; la) is expected to be useful as an oral therapeutic agent for muscular dystrophy on the basis of its potent inhibitory activities against the cysteine proteinases involved in the myofibrillar protein degradation that occurs in the disease. Through extensive investigations aimed at developing a new synthetic method for la that would be suitable for industrial application, it has been found that L-arginine can be used as a new, efficient resolving agent to obtain optically pure L-trans-epoxysuccinic acid (3a), and the active ester method using p-nitrophenol is very effective in the coupling reaction of ethyl L-trans-epoxysuccinate (7a) and L-leucine isoamylamide (8a) because of the extremely low formation of by-products.To examine the contribution of the stereochemistry of the trans-epoxysuccinic acid and leucine moieties to the inhibitory activity against cysteine proteinases, the diastereomers (lb-d) of la were synthesized by a similar method and the rate constants of inactivation of papain by la-d were measured. Compound la, having L-trans-epoxysuccinic acid and L-leucine moieties, showed the most potent activity among them.

A basic protein with a molecular weight of approximately 10,100 and having a single atom of Type I copper has been isolated from cucumber seedlings. The oxidized, cupric, form of the protein has been crystallized as thin olive-green plates with space group P 2 1 2 1 2 1 and cell dimensions a = 30.8 A, b = 45.6 A and c = 66.6 A. There is one protein molecule per asymmetric unit.

The reactions of poplar plastocyanin, PCu(I), with [Fe(CN)6]3– and [Co(phen)3]3+(phen = 1,10-phenanthroline) as oxidants, and of PCu(II) with [Co(phen)3]2+ as reductant, have been studied at 25 °C, I= 0.10 M (NaCl). At pH 7.5, 69% of the reaction of [Co(phen)3]3+ is at the Tyr 83 site, which incorporates the acidic patch, in this case at 42–44. With [Fe(CN)6]3– as oxidant the behaviour observed is consistent with reaction at the His 87 (north) site. From the effects of pH (4.5–7.5) on rate constants, active site (pKa 4.7) and (acidic patch) binding site (pKa′ 5.25) deprotonation/protonation equilibria are identified. For PCu(II) no active site pKa is observed, and the binding site pKa′ is 5.1. Comparisons are made with plastocyanin from parsley, spinach, and French bean. With [Co(phen)3]3+ as oxidant no limiting kinetic behaviour is observed, and association of PCu(I) with [Co(phen)3]3+ is at a lower level (K < 50 M–1). From competitive inhibition studies association with redox inactive [(NH3)5Co(NH2)Co(NH3)5]5+ is also at a lower level (K= 5 650 M–1). The origin of differences in pKa′ for PCu(I) and PCu (II) states is discussed.