Continuous assay of protein tyrosine phosphatases based on fluorescence resonance energy transfer

An assay method that continuously measures the protein tyrosine phosphatase (PTP)-catalyzed dephosphorylation reaction based on fluorescence resonance energy transfer (FRET) was developed as an improvement of our previously reported discontinuous version [M. Nishikata, K. Suzuki, Y. Yoshimura, Y. Deyama, A. Matsumoto, Biochem. J. 343 (1999) 385-391]. The assay uses oligopeptide substrates that contain (7-methoxycoumarin-4-yl)acetyl (Mca) group as a fluorescence donor and 2,4-dinitrophenyl (DNP) group as a fluorescence acceptor, in addition to a phosphotyrosine residue located between these two groups. In the assay, a PTP solution is added to a buffer solution containing a FRET substrate and chymotrypsin. The PTP-catalyzed dephosphorylation of the substrate and subsequent chymotryptic cleavage of the dephosphorylated substrate results in a disruption of FRET, thereby increasing Mca fluorescence. In this study, we used FRET substrates that are much more susceptible to chymotryptic cleavage after dephosphorylation than the substrate used in our discontinuous assay, thus enabling the continuous assay without significant PTP inactivation by chymotrypsin. The rate of fluorescence increase strictly reflected the rate of dephosphorylation at appropriate chymotrypsin concentrations. Since the continuous assay allows the measurement of initial rate of dephosphorylation reaction, kinetic parameters for the dephosphorylation reactions of FRET substrates by Yersinia, T-cell and LAR PTPs were determined. The continuous assay was compatible with the measurement of very low PTP activity in a crude enzyme preparation and was comparable in sensitivity to assays that use radiolabeled substrates.

A new method for evaluating the bitterness of medicines by semi-continuous measurement of adsorption using a taste sensor

We describe a new method for the evaluation of the bitterness of medicines by semi-continuous measurement of adsorption using a multichannel taste sensor or 'electric tongue'. The bitterness of 10 basic medicines was evaluated by both the taste sensor and in human gustatory sensation tests with 11 volunteers. The sensor part of the taste sensor consists of eight electrodes made of lipid/polymer membranes. Three variables were obtained from the taste sensor data: sensor output (S), the change of membrane potential caused by adsorption, corresponding to aftertaste (C), and the ratio C/S. These variables were used to predict an estimated bitterness score in multiple regression analysis. Semi-continuous measurement of C (every 30 s up to 150 s) was adopted as an additional explanatory variable, and the attenuation rate of C was defined as C'. These data were also subjected to multiple regression analysis. The correlation coefficient (r) estimated for the bitterness score predicted by the taste sensor, using C' for channel 2 and C/S for channel 4, and the score obtained by human gustatory sensation, was 0.824. This value was greater than that obtained using C/S for both channels 2 and 4 (0.734). The method described in the present study seems to offer good predictability for the evaluation of bitterness.

Preparation and characterization of insulin-loaded acrylic hydrogels containing absorption enhancers

The objectives of this study were to prepare insulin-loaded acrylic hydrogel formulations containing various absorption enhancers, to perform in vitro and in vivo characterization of these formulations, and to evaluate the factors which affecting insulin availability on rectal delivery of insulin using this hydrogel system. The acrylic block copolymer of methacrylic acid and methacrylate, Eudispert, was used to make the hydrogel formulations. As absorption enhancers, 2,6-di-O-methyl-beta-cyclodextrin (DM-beta-CyD), lauric acid (C12), or the sodium salt of C12 (C12Na), were incorporated into the hydrogels. In an in vitro release test, the release rate of insulin from the hydrogels decreased as the polymer concentration of the hydrogel increased. The addition of C12Na to the hydrogel further increased the insulin release rate, which was greater at higher concentrations of the enhancer. A portion of the C12Na was found to remain bound to the acrylic polymer in dissolution medium. Serum insulin levels were determined at various time points after the administration of insulin solution or insulin-loaded (50 units/kg body weight) Eudispert hydrogels containing 5% (w/w) of C12, C12Na, or DM-beta-CyD to in situ loops in various regions of the rat intestine. The most effective enhancement of insulin release was observed with formulations containing C12Na. The bioavailability of insulin from the hydrogels was lower than that from the insulin solutions. Hydrogel formulations containing 7% or 10% Eudispert remained in the rectum for 5 h after rectal administration. However, the 5% (w/w) C12Na solution stained with Evan's-blue had diffused out and the dye had reached the upper intestinal tract within 2 h. Finally, the rectal administration of insulin-loaded hydrogels, containing 4%, 7%, or 10% (w/w) Eudispert and 5% (w/w) of enhancer (C12, C12Na, or DM-beta-CyD) to normal rats was shown to decrease serum glucose concentrations. The greatest effect was found with insulin-loaded 7% (Eudispert) hydrogel containing C12Na which having cosiderable large insulin release rate and bioadhesive characteristics.

Inactivation of NF-kappaB involved in osteoblast development through interleukin-6

Osteoblasts undergo a process of proliferation and differentiation and are responsible for bone formation. In this study, we examined the relation between NF-kappaB, a key transcription factor in bone metabolism, and osteoblast maturation. NF-kappaB activity and expression of p50, a subunit of NF-kappaB, decreased during development of osteoblastic MC3T3-E1 cells. The secretion of IL-6 by osteoblast, which in combination with soluble IL-6 receptor induces conversion of fibroblasts to alkaline phosphatase-positive cells, also increased. p50 antisense oligonucleotide increased IL-6 mRNA expression. These results suggest that p50 regulates transcription of IL-6 and indirectly controls osteoblast maturation.

Osteoblast maturation suppressed osteoclastogenesis in coculture with bone marrow cells

The analysis of co-culture system using osteoblast and bone marrow indicated that the mineralized osteoblast decreased osteoclast formation. This finding was an incentive to better investigate the relation of osteoblast development and osteoclastogenesis. The expression of osteoclast differentiation factor (ODF/RANKL) mRNA and protein dramatically decreased. Alternatively, macropharge colony stimulation factor (M-CSF/CSF-1) transcription and protein secreted in media slightly decreased as the development of osteoblast. On the other hands, mRNA expression and the secretion to the culture medium of osteoclastogenesis inhibitory factor (OPG/OCIF) didn't significantly change depending on osteoblast differentiation. We conclude that osteoblast development might suppress osteoclastogenesis especially with the decrease of ODF/RANKL.

T-kininogen and a 45 kda proteinase from Porphyromonas gingivalis

To clarify the pathogenic role of proteinases from Porphyromonas gingivalis, a 45 kDa proteinase was isolated from P. gingivalis culture medium by a combination of gel filtration (Bio-Gel A-0.5 m) and ion-exchange chromatographies (DEAE-Sephacel and SP-Sepharose FF). The enzyme was found to have a molecular mass of 45 kDa by SDS-PAGE and to require mercaptoethanol for its activation. The 45 kDa proteinase cleaved T-kininogen into small fragments, but failed to release kinin. In contrast, T-kininogen inhibited the Arg-amidolytic activity of the 45 kDa proteinase with a Ki of 2 nM. On the other hand, the 45 kDa proteinase did not stimulate the production of PGE2, IL-1beta, and TNF-alpha from the macrophages.

A phosphotyrosine-containing quenched fluorogenic peptide as a novel substrate for protein tyrosine phosphatases

Mca-Gly-Asp-Ala-Glu-Tyr(PO(3)H(2))-Ala- Ala-Lys(DNP)-Arg-NH(2), where Mca is (7-methoxycoumarin-4-yl)acetyl and DNP is 2,4-dinitrophenyl, was synthesized as a fluorogenic substrate for protein tyrosine phosphatases (PTPs). In the peptide, the fluorescent Mca group is quenched efficiently by the DNP group. Although the fluorescence intensity of the substrate was practically unchanged upon PTP-catalysed dephosphorylation, it increased approx. 120-fold upon subsequent treatment with chymotrypsin. Analysis by HPLC showed that chymotrypsin cleaved only the dephosphorylated substrate at the Tyr-Ala bond. Thus with the aid of chymotrypsin, dephosphorylation of the substrate can be measured fluorometrically. A strictly linear correlation was observed between PTP concentration and dephosphorylation rate. The fluorogenic substrate was dephosphorylated by some PTPs much more rapidly than the corresponding (32)P-labelled substrate used for comparison, whereas alkaline phosphatase dephosphorylated the two substrates at similar rates. The fluorogenic substrate is therefore more specific for PTPs than the radiolabelled substrate. The assay with the fluorogenic substrate could be applied to the estimation of kinetc parameters and measurement of PTP activity in crude-enzyme preparations. The lower detection limit of our assay (1 microM substrate in 200 microliter of reaction mixture) was estimated to be 0.2-0.4 pmol, whereas it was estimated to be about 1 pmol in the assay that used (32)P-labelled peptide (specific radioactivity of approx. 1000 c.p.m. /pmol). Our assay is simple, specific, highly sensitive and non-radioisotopic, and hence would contribute greatly to the development of PTP biology.

A low calcium environment enhances AP-1 transcription factor-mediated gene expression in the development of osteoblastic MC3T3-E1 cells

Animals fed a low calcium diet develop hypocalcemia and osteoporotic bone. Earlier we conjectured that a low calcium environment might be one of the factors causing abnormalities in hard tissues. Osteoblastic MC3T3-E1 cells (E1 cells) undergo a process of proliferation and differentiation and then produce small mineralized nodules. In this study, we examined the effects of a low calcium environment on osteoblast-like cells cultured with 10% fetal bovine serum and ascorbic acid. Under the culture condition, nodules with characteristics of normal bone appeared by day 30 regardless of the calcium conditions. However, the low calcium environment enhanced the mRNA expressions of c-fos, c-jun and osteocalcin, a specific marker of the osteoblast phenotype. And the exposure to the low calcium medium inhibited the formation of bone nodules. We further studied the differential expressions of c-fos and c-jun in relation to their responses to serum as a function of phenotypic development in the low calcium environment. Both c-fos and c-jun expressions were highly activated by treatment with epidermal growth factor (EGF), but the magnitude of activation was significantly larger under the low calcium condition than the normal condition at each stage. In addition, DNA-binding activities of activating protein-1 (AP-1), Fos/Jun family dimers, were also accelerated by EGF treatment in the low calcium environment. Our findings suggested that osteocalcin, a bone formation marker, c-fos and c-jun genes, and family protein products (AP-1) interacted to restore the normal cell function which deteriorated in the low calcium environment.

Early potentials of direct cortical responses: experimental study in dogs and pathophysiological and clinical implications

OBJECTIVE

The characteristics of the early component of the direct cortical response have not been well studied, although direct cortical response recording is a common method of brain function monitoring.

METHODS

In this experimental study, we sought conditions affording the clearest recording of the early potential, by varying the polarity and low-cutoff filter setting, and we confirmed that the early potential consists of two components, P1 and P2.

RESULTS

When subcortical damage was induced by local cerebral compression or saline injection, transient changes in P1 and permanent disappearance of P2 were observed. P2 also disappeared when the fiber connections between the cortex and the basal ganglia, including the thalamus, were destroyed by wire insertion. With deep recording, both P1 and P2 exhibited potential reversal at a level histologically confirmed to be in Layer V of the cortex.

CONCLUSION

These findings suggest that P1 is a spike reflecting the activity of pyramidal cells evoked by electrical stimulation of the brain surface and that P2 is a potential arising in Layer V of the cortex and is related to afferent fibers from the thalamus. Recording of P2 may be useful for monitoring for subcortical damage.

Preparation and characterization of polylactic acid microspheres containing bovine insulin by a w/o/w emulsion solvent evaporation method

The objective of this study was to produce polylactic acid (PLA) microspheres containing bovine insulin as a sparingly water soluble model drug using a water-in-oil-in-water (w/o/w) emulsion solvent evaporation method. The preparative conditions were optimized. Employment of smaller internal aqueous phase volume (50 microliters or 100 microliters) in the manufacturing process, resulted in the high loading efficiency (over 95% of theoretical insulin loading efficiency). The addition of 10% (w/v) NaCl to the external aqueous phase (0.5% polyvinyl alcohol solution) reduced loading efficiency compared to the case where no NaCl was added to the external phase. The mean volume diameter for prepared PLA microspheres was in the region of 15-25 microns in all cases. PLA microspheres containing 5% and 10% insulin theoretically exhibited burst release in the initial stage. After a three week dissolution test, the surface of the microspheres became more porous due to the degradable characteristics of PLA polymer itself. Nevertheless, about 80% of the insulin still remained undegraded in PLA microspheres. Finally, insulin-loaded PLA microspheres (corresponding to 4 I.U. insulin) were administered to normal rats subcutaneously, and the pharmacological effect (a decrease in serum glucose level) was demonstrated.

Enhanced myopathy following administration of hypolipidemic agents under urethane anesthesia

The enhanced effect of urethane anesthesia on the serum creatine kinase (CPK) level following administration of hypolipidemic agents was examined to develop a convenient experimental screening method for drug-induced myopathy. After oral administration of a hypolipidemic agent to rats, 25% urethane solution was infused intravenously at a very low rate using a microinfusion pump. Blood samples were collected 7 h after drug administration and the risk of myopathy was evaluated based on the CPK level. When bezafibrate (BF), simvastatin (SV), or pravastatin (PV) (50-500 mg/kg) was orally administered under urethane infusion, enhanced elevation of the serum CPK level was observed dose dependently for BF and SV, but not for PV. The elevation of serum CPK was much higher with BF than with SV or PV. In addition, when SV or PV (50-500 mg/kg) was coadministered with 50 mg/kg of BF, there was a striking increase in the serum CPK level as compared with the drug alone. Without urethane infusion, no significant elevation in serum CPK level was observed even at a high dose of these hypolipidemic agents. These phenomena suggest that the urethane anesthesia enhanced the elevation of the serum CPK level following administration of hypolipidemic agents. We propose that this method is a simple and speedy screening test for drug-induced myopathy.

Drug interaction between simvastatin and cholestyramine in vitro and in vivo

The interaction between simvastatin (SV), a prodrug lactone, HMG-CoA reductase inhibitor which converts to the active hydroxy acid form (SVH) in vivo, and cholestyramine (CT), an anionic exchange resin, was evaluated both in vitro and in vivo. In an in vitro SV-stability study, it was shown that SV degraded gradually to SVH in an aqueous solution at pH 2 and 7. To evaluate the binding ability of SV or SVH to CT, the incubation of 5 micrograms/ml of SV or SVH solution with 200 mg of CT in various pH (2.0, 5.0 and 7.0) solutions was performed at 37 degrees C for 10 min. After incubation, the concentration of SV decreased by 59.02% (pH 2), 63.90% (pH 5) and 67.36% (pH 7), respectively, and an interaction between SV and CT was suggested. The values were much larger than those expected from the stability test of SV in the absence of CT. SVH was found to bind more strongly to CT. The binding ability of SVH to CT was 66.71% (pH 2), 87.44% (pH 5) and 92.11% (pH 7), respectively. Judging from these results, SV was considered to interact with CT by the following procedure: SV underwent hydrolysis to SVH in aqueous solution, then CT activated the hydrolysis by binding the formed SVH, resulting in a significant reduction in concentration of SV. On the other hand, an in vivo animal experiment also demonstrated a significant reduction (about 50% with AUC) in the concentration of SVH in plasma following the coadministration of SV (500 mg/kg p.o.) and CT (600 mg/kg p.o.), compared with the administration of SV alone. This phenomenon suggested that a combination therapy using SV and CT might result in a smaller cholesterol-lowering effect of SV.

Active site structure of a hemagglutinating protease from Porphyromonas gingivalis: similarity to clostripain

The active site of a 44-kDa hemagglutinating arginine-specific protease from the putative periodontopathogen Porphyromonas gingivalis was specifically labeled with N alpha-[3H]acetyllysine chloromethyl ketone. After enzymatic digestion of the labeled enzyme, a labeled active site peptide was isolated by HPLC. The sequence of the active site peptide was determined, after its treatment with NaBH4 to reduce the ketone group of the reagent moiety, to be Asp-Val-Ala-Cys-Val-Asn-Gly. The cysteine residue was found to be the site for labeling. The sequence resembled the active site structure of the arginine-specific cysteine protease clostripain from Clostridium histolyticum.

Effect of first-pass metabolism on enantioselective pharmacokinetics after oral administration of (+)-, (-)- and racemic homochlorcyclizine to rats

The enantioselective relationship between the pharmacokinetics and hepatic metabolism of homochlorcyclizine hydrochloride (HCZ) was investigated using rats. There were no significant differences in blood concentrations between the three forms after intravenous administration (5 mg/kg) of (+)-, (-)- and racemic HCZ. On the other hand, there were significant differences in the pharmacokinetics between (-)- and (+)-HCZ and between (-)- and racemic HCZ after oral administration (50 mg/kg) of these three forms. The Cmax and AUC0-infinity of (-)-HCZ were lower than those of (+)-isomer and racemate, and its CLo was clearly higher than the others. The (+)-isomer and racemate showed no significant differences in their pharmacokinetic parameters. At a lower dose (10 mg/kg), however, no enantiomeric differences were found in the pharmacokinetic parameters of (+)- and (-)-HCZ. Also examined was the cytochrome p-450-dependent-oxidative metabolism of (+)-, (-)- and racemic HCZ in vitro using rat liver 9000 x g supernatant fraction. The in vitro metabolism of (-)-HCZ was extremely fast, compared with those of the (+)-isomer and the racemate. The Vmax in vitro showed a good correlation with the CLo in vivo after oral administration (50 mg/kg) of all three forms of HCZ. In vitro study of enantiomeric inhibition of the metabolism showed that (+)-HCZ was a competitive inhibitor of (-)-HCZ metabolism, with a Ki of 6.96 microM. (-)-HCZ was also a competitive inhibitor of (+)-HCZ metabolism, with a Ki of 20.4 microM.(ABSTRACT TRUNCATED AT 250 WORDS)

Purification and characterization of two forms of a high-molecular-weight cysteine proteinase (porphypain) from Porphyromonas gingivalis

Porphyromonas gingivalis, and organism implicated in the etiology and pathogenesis of human periodontal diseases, produces a variety of potent proteolytic enzymes, and it has been suggested that these enzymes play a direct role in the destruction of periodontal tissues. We now report that two cell-associated cysteine proteinases of P. gingivalis W12, with molecular masses of approximately 150 kDa (porphypain-1) and 120 kDa (porphypain-2), as determined by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis, have been separated and purified to apparent homogeneity. These proteinases appear to be SDS-stable conformational variants of a 180-kDa enzyme, and they are the largest cysteine proteinases yet purified from P. gingivalis. The purified proteinases hydrolyze fibrinogen, tosyl-Gly-L-Pro-L-Arg p-nitroanilide, and tosyl-Gly-L-Pro-L-Lys p-nitroanilide. While hydrolysis of both synthetic substrates by porphypain-1 and -2 requires activation by reducing agents, is inhibited by EDTA, and is stimulated in the presence of derivatives of glycine, the Arg-amidolytic activity is sensitive to leupeptin and H-D-tyrosyl-L-prolyl-L-arginyl chloromethyl ketone, whereas the Lys-amidolytic activity is sensitive to tosyl-L-lysyl chloromethyl ketone and insensitive to leupeptin. These data suggest that porphypains contain two types of active sites. These cell-associated P. gingivalis proteinases may contribute significantly and directly to periodontal tissue destruction.

Enantioselective pharmacokinetics of homochlorcyclizine: disposition of (+)- and (-)-homochlorcyclizine after intravenous and oral administration of racemic homochlorcyclizine to rats

Concentrations of homochlorcyclizine enantiomers in blood, urine, and tissues of the liver, lung, kidney, brain, heart, spleen, intestine and stomach of rats after drug administration were determined by high-performance liquid chromatography on a chiral stationary phase. After intravenous administration (10 mg kg-1), homochlorcyclizine was rapidly distributed in many tissues, with the highest concentration in lung. No differences were found between enantiomers in blood concentrations. After oral administration (50 mg kg-1), the concentrations of the (+)-isomer in nearly all tissues were higher than those of the (-)-isomer. The AUC0-infinity values of the (+)- and (-)-isomers differed significantly. The absorption of racemic homochlorcyclizine from rat small intestine was not enantioselective. These results suggested that the different concentrations between enantiomers after oral administration were not caused by enantioselective absorption or distribution but rather by preferential first-pass metabolism of the (-)-isomer in the liver. The enantioselectivity of metabolism was also demonstrated by in-vitro experiments.

Synthesis of N alpha-[3H]acetyl-L-lysine chloromethyl ketone and its use in the fluorographic detection of proteases

Tritiated N alpha-acetyl-L-lysine chloromethyl ketone (ALCK) was synthesized on a laboratory scale for use as an active-site-directed affinity label in the fluorographic detection of proteases after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The synthesis involved acetylation of N epsilon-benzyloxycarbonyl-L-lysine chloromethyl ketone with [3H]acetic anhydride just before the removal of the benzyloxycarbonyl group. By this method, [3H]ALCK with a specific activity of 250 mCi/mmol was obtained as a crystal. Trypsin, thrombin, plasmin, papain, and clostripain were inactivated by ALCK according to first-order kinetics. For fluorographic detection of proteases, enzyme samples were allowed to react with [3H]ALCK and then resolved by SDS-PAGE. Proteases that reacted with [3H]ALCK could be detected with a sensitivity equivalent to or higher than that of Coomassie brilliant blue R-250 staining. A trypsin-like protease in Pronase, clostripain as a contaminant in a commercial preparation of Clostridium histolyticum collagenase, and cysteine proteases in Porphyromonas gingivalis could be detected.

Enantioselective pharmacokinetics of homochlorcyclizine. III. Simultaneous determination of (+)- and (-)- homochlorcyclizine in human urine by high-performance liquid chromatography

A method is described for the simultaneous determination of (+)- and (-)-homochlorcyclizine (HCZ) in human urine by high-performance liquid chromatography on a chiral stationary phase of ovomucoid-bonded silica. The pH of the buffer and organic modifier in the mobile phase markedly affected the chromatographic separation. A mobile phase of methanol-0.02 M acetate buffer (pH 4.7) (25:75,v/v) at a flow-rate of 1.0 ml/min was used for the urine assays. The ultraviolet absorption was monitored at 240 nm, and diphenhydramine was employed as the internal standard for the quantitation. (+)-HCZ, (-)-HCZ and the internal standard were eluted at retention times of 15, 25 and 8 min, respectively. The limit of determination for HCZ enantiomers was ca. 50 ng/ml of urine. One of the metabolites in human urine, which was a quaternary ammonium-linked glucuronide, could also be determined in a manner similar to unchanged HCZ after beta-glucuronidase hydrolysis. A pharmacokinetic study was conducted with three healthy volunteers, who each received a single oral dose of racemic HCZ (20 mg). Distinct differences were found between the two enantiomers, particularly in the metabolic process, that is, the urinary excretion as (-)-HCZ-glucuronide within 48 h was ca. four times higher than that of the (+)-isomer. This method should be very useful for enantioselective pharmacokinetic studies of HCZ.

Enantioselective pharmacokinetics of homochlorcyclizine II: disposition and metabolism of (+)-, (−)- and racemic homochlorcyclizine after oral administration to man

The pharmacokinetics of a single oral dose of 20 mg (+)-, (-)- and racemic homochlorcyclizine (HCZ) have been studied in humans. The formation of the quarternary ammonium-linked glucuronide was an important metabolic pathway, and the metabolic process was enantioselective as a result of differing urinary excretion rates of (+)-, (-)- and racemic glucuronide. There were significant differences between (+)-, (-)- and racemic HCZ in AUC (0-14 h) and plasma protein binding, but all HCZ enantiomers were slowly absorbed and eliminated (elimination half-lives about 11 h). The results shows help to establish a more efficient dosage regimen for HCZ therapy.

Effect of gastrointestinal maturation on absorption of beta-lactam antibiotics

Gastrointestinal absorption of cefazolin, which is poorly absorbed in adults, and of cephradine, which is well absorbed in adults, was studied in rats during their development. Significantly higher concentrations of cefazolin in plasma after oral administration were observed in 1- and 2-week-old rats compared with 3-week-old and adult rats. A marked difference in the absorption of cefazolin by 2- and 3-week-old rats (at weaning period) was observed. No such marked difference in the absorption of cephradine by rats of various age groups was found. With cefazolin, a similar pattern of developmental change in jejunal uptake was observed. Cortisone, which causes early maturation of the intestinal membrane, was given as a preweaning injection to 2-week-old rats. This treatment decreased concentrations of cefazolin in plasma and jejunal uptake of cefazolin. Thus, the absorption of cefazolin in 1- and 2-week-old rats seems to depend on the permeability of the immature intestinal membrane before weaning. Cephradine absorption from the intestine of 1-week-old rats became saturated and inhibited by carnosine and glycylglycine when studied by the in situ loop method. Cefazolin absorption was proportional to luminally administered doses and was not affected by carnosine and glycylglycine. A nonsaturable process for cefazolin and a saturable process for cephradine were also observed in an in vitro uptake experiment.

Method for Optical Resolution of Racemic Homochlorcyclizine and Comparison of Optical Isomers in Antihistamine Activity and Pharmacokinetics

A method was developed for semi-preparative scale enantioseparation of racemic homochlorcyclizine (HCZ) by high performance liquid chromatography (HPLC) on Chiralcel OD column. The best resolution was achieved using an eluent composed of n-hexane plus 0.2 M isopropylamine. By this method, about 5.0 mg of racemic HCZ could be resolved completely in one run. The optical purity of the enantiomers were both greater than 99.9%. The studies of antihistamine activity on guinea pig ileum demonstrated that l-HCZ is significantly more potent than d- and racemic HCZ. The pharmacokinetics of d- and l-HCZ after oral administration to rats also differed. The successful resolution of racemic HCZ permits comparison of the pharmacokinetics and antihistamine activity of the enantiomers.

Characterization of Porphyromonas (bacteroides) gingivalis hemagglutinin as a protease

A hemagglutinin (HA) was purified to homogeneity from the membrane fraction of the oral bacterium Porphyromonas gingivalis. The HA possessed protease activity hydrolyzing proteins and arginine-containing synthetic substrates. The protease activity was inhibited by thiol-blocking reagents, and hence the HA can be characterized as a cystein protease. The HA functions as an attachment factor and its substrate-binding site is responsible for the attachment to an erythrocyte.

Involvement of prolyl endopeptidase in ascidian fertilization

Inhibitory effects on fertilization of the ascidian of three benzyloxycarbonyl(Z)-aminoacyl prolinals and Z-Gly-Pro-chloromethyl ketone added before and after insemination were examined. The results suggest that the prolyl endopeptidase is involved in the process of fertilization, especially in a process taking place between chorion elevation and cell cleavage.

Possibility of Bacteroides gingivalis hemagglutinin possessing protease activity revealed by inhibition studies

Inhibition of hemagglutinin (HA) activity in a membrane fraction of Bacteroides gingivalis was examined using various compounds. Leupeptin and anti-pain inhibited the HA activity at nM order. This potency was lost when the aldehyde group of leupeptin was converted to an alcohol moiety. Irreversible protease inhibitors, tosyl-L-lysine chloromethyl ketone (TLCK), p-chloromercuribenzoate (PCMB), and N-ethylmaleimide (NEM) were also inhibitory. From the inhibition experiments, we speculate that the HA possesses protease activity and that the same site of the molecule participates in the erythrocyte binding and the substrate binding.

Gastrointestinal absorption of sulfaguanidine in neonatal and adult rats

The pharmacokinetics of sulfaguanidine in rats was studied after its intravenous or oral administration. In adult rats, its elimination from plasma, after intravenous administration of 2.5 or 25 mg/kg doses, could be described by a two-compartment open model, while its plasma concentration after oral administration of 25 mg/kg doses, agreed with the one- or two-compartment open model. Neonatal rats displayed a lower elimination of sulfaguanidine than adult rats. Comparison of the drug's gastrointestinal absorption showed that the maximum plasma concentration after oral administration was significantly higher for neonatal than for adult rats. However, there was no significant difference between the times required to reach maximum plasma concentrations. The area under the plasma concentration-time curve at 0-infinity h was significantly higher for neonatal than for adult rats. The absolute bioavailability (57.86%) in neonatal rats was approximately five times that (12.76%) in adult rats. Thus, sulfaguanidine was poorly absorbed by adult rats, but was efficiently absorbed by immature gastrointestines of neonatal rats.

Gastrointestinal absorption of sulpiride in rat

A two-compartment model could be used to describe the elimination of sulpiride from plasma after intravenous administration of 25 and 50 mg/kg doses to rat. The absolute bioavailability after oral administration was only about 15% which was also the level after intraduodenal administration. Higher bioavailabilities were found after mesenteric venous and intravenous administration (sham-operated rat) due to a decrease in the beta-value (elimination rate constant). The low bioavailability of sulpiride following oral administration was concluded to result, not from metabolism in the liver, but from reduced absorption by the gastrointestinal tract.

Inhibition studies of soybean trypsin-like enzyme

The results of inhibition studies of soybean trypsin-like enzyme (STLE) by substrate analogues (derivative of arginine) suggested that a net negative charge exists at or near the substrate binding region of the enzyme. On hydrolysis of substrates, this negative charge seems to repel the products from the substrate binding region and facilitate the turn-over of substrates. From the data on inhibition by various amidines, guanidines, and amines, some information about the structure of the hydrophobic binding pocket of STLE was obtained. The inactivation of STLE by irreversible inhibitors, diisopropylfluorophosphate (DFP) and tosyl-lysine chloromethyl ketone (Tos-Lys-CH2Cl), was decreased by competitive inhibitors. This means that these irreversible inhibitors bind with residues at the substrate binding region, probably serine and histidine residues, respectively.

Kinetic investigation of soybean trypsin-like enzyme catalysis

Various esters and amides of benzoylarginine and of benzyloxycarbonylarginine were subjected to enzymic hydrolysis at pH 8.5 and 7.2 by soybean trypsin-like enzyme (STLE). The kcat values for the hydrolysis of esters and amides were essentially identical regardless of the kind of leaving group. These results suggest that the STLE-catalyzed hydrolysis of ester and amide substrates proceeds via an acylenzyme intermediate and that the deacylation step is rate-determining. Hydrolysis of various 4-methylcoumaryl-7-amides of varying chain length and amino acid sequence was carried out at pH 8.5. Analysis of kinetic parameters revealed that STLE does not exhibit any remarkable subsite requirement, but somewhat preferentially hydrolyzes shorter substrates. These observations are consistent with the fact that STLE does not hydrolyze protein substrates or oxidized insulin B chain but hydrolyzes oligopeptides (Nishikata, M. (1984) J. Biochem. 95, 1169-1177). It is possible that the active site of STLE is located at a deep position in the enzyme molecule. From the pH dependency of kcat/Km, the participation of a histidine residue in the catalytic process of STLE was suggested.

N-Benzyloxycarbonyl-valyl-prolinal, a potent inhibitor of post-proline cleaving enzyme

A peptide aldehyde inhibitor possessing prolinal at the carboxyl terminus was designed as an inhibitor of post-proline cleaving enzyme by analogy with peptide aldehyde inhibitors of serine and thiol proteases. N-Benzyloxycarbonyl-valyl-prolinal was found to be a potent inhibitor of post-proline cleaving enzyme from ascidian sperm with a K1 value of 2.4 nM. The presence of the aldehyde portion of the inhibitor, as well as its prolonged incubation with the enzyme, is indispensable for the potent inhibitory activity of the inhibitor. These results indicate that N-benzyloxycarbonyl-valyl-prolinal functions as a transition-state aldehyde inhibitor of post-proline cleaving enzyme.

Trypsin-like protease from soybean seeds. Purification and some properties

An enzyme was purified from soybean seeds mainly by repeated ion-exchange chromatography using benzoyl-L-arginine p-nitroanilide (BAPA) as a substrate. The purified enzyme was homogeneous as judged by disc gel electrophoresis. The molecular weight was estimated as 59,000 by gel filtration. The enzyme was most active toward BAPA between pH 8 and 10. The enzyme was inactive toward protein substrates but hydrolyzed synthetic substrates and oligopeptides exclusively at the carboxyl side of L-arginine and L-lysine. Kinetic studies using synthetic substrates showed that, on the basis of Vmax/Km, the enzyme preferentially hydrolyzed amide substrates over ester substrates. Benzoyl-L-arginine 4-methylcoumaryl-7-amide (Bz-Arg-MCA) was the best substrate. The enzyme was strongly inhibited by diisopropylfluorophosphate (DFP), tosyl-L-lysine chloromethyl ketone (Tos-Lys-CH2Cl), leupeptin, and antipain. p-Chloromercuribenzoate (PCMB) was only partially inhibitory. Various protein inhibitors of trypsin such as soybean trypsin inhibitor were ineffective. From the primary specificity and susceptibility to chemicals, the enzyme can be said to be a trypsin-like serine protease. Although the physiological role of the enzyme is unclear, it seems likely that it is involved in limited hydrolysis of certain physiological peptides during processing.

Characterization of a trypsin-like protease from the bacterium Bacteroides gingivalis isolated from human dental plaque

A trypsin-like, membrane-bound protease from Bacteroides gingivalis was solubilized by Triton X-100 and partially purified by a combination of DEAE-Sepharose and aminophenylmercuric Sepharose chromatography, by taking advantage of the thiol group on the enzyme. The purified enzyme hydrolysed the synthetic substrates benzoyl-L-arginine-p-nitroanilide (L-BAPA), benzoyl-D,L-arginine-beta-naphthylamide (BANA) and tosyl-L-arginine methyl ester, as well as bovine serum albumin and ovalbumin, but not tosyl-L-lysine methyl ester. The enzyme activity was enhanced by SH-reagents and was inhibited to different degrees by SH-inhibitors, chelators and microbial low-molecular-weight inhibitors such as leupeptin, antipain and chymostatin. These microbial inhibitors could be of practical use as ligands for affinity chromatography for further purification. The possible involvement of the protease in periodontal diseases is also discussed.

Affinity chromatography of chymotrypsin on a sepharose derivative coupled with a chymostatin analogue

A Sepharose derivative coupled with a chymostatin analogue, Gly-Gly-L-Leu-L-phenylalaninal (Pheal), was prepared. A number of native and chemically modified proteases were applied on a column of the adsorbent. Bovine chymotrypsins [EC 3.4.21.1] and Streptomyces griseus protease B were adsorbed strongly at pH 8.2. The affinities of these enzymes under various conditions were measured quantitatively by frontal chromatography in terms of the dissociation constant (Kd) of the enzyme-immobilized ligand complex. The pH dependence of the Kd value of alpha-chymotrypsin was consistent with that of the inhibition constant (Ki) of the enzyme for a corresponding soluble peptide aldehyde. Anhydro-chymotrypsin, in which the active site Ser-195 is converted to dehydroalanine, was not adsorbed. Ser-195 proved to be essential for the binding. The frontal chromatography method also gave the amount of the immobilized ligand that can interact with the enzyme. It was extremely small compared with the amount of the immobilized ligand determined by amino acid analysis. This was explained on the basis of the structural features of the agarose gel.

A sepharose derivative coupled with a leupeptin-like peptide aldehyde, glycylglycyl-L-argininal, and its use as an affinity adsorbent for trypsin

A Sepharose derivative containing a peptide aldehyde, glycylglycyl-L-argininal, the structure of which resembles that of leupeptin was prepared. It was a strong affinity adsorbent for trypsin (EC 3.4.21.4). Bovine trypsin showed higher affinity for this adsorbent at the optimum pH of catalysis (8.2) than at lower pH (5.0). This observation was in good agreement with the pH dependence of the interaction of leupeptin and trypsin (Kuramochi, H., Nakata, H. and Ishii, S. (1979) J. Biochem. 86, 1403-1410). Streptomyces griseus trypsin was also adsorbed while trypsinogen, alpha-chymotrypsin and TLCK-trypsin were not adsorbed. Though anhydrotrypsin, in which Ser-183 is converted to dehydroalanine, was not adsorbed, carbamoylmethylated (His-46) trypsin was adsorbed. Ser-183 proved to be essential for the binding. This adsorbent can also be used as a good tool to study the mechanism of action of leupeptin.

Affinity chromatography of trypsin and related enzymes. IV. Quantitative comparison of affinity adsorbents containing various arginine peptides

In order to study the mechanism of substrate binding of trypsin by affinity chromatography, we synthesized various L-arginine-terminated oligopeptides having different chain length and amino acid sequences, and immobilized them on agarose gel. The interaction of beta-trypsin with these adsorbents was studied by a quantitative affinity chromatographic procedure which gave the dissociation constant (Kd) of the trypsin-immobilized ligand complex. This procedure proved to be very useful and to give information equivalent to that obtained by kinetic procedures. The contribution of the amino acid residue at P2 of the ligands to the affinity was studied by using tripeptide (Gly-X-Arg) Sepharoses, and alanine was found to be more effective than glycine or valine. This conclusion was supported by a kinetic experiment in which Ki values of the corresponding soluble tripeptides (Ac-Gly-X-Arg) were determined. A significant decrease in Kd was observed when the ligand was elongated from dipeptide to tripeptide. However, Kd decreased only slightly when the ligand was elongated further. This suggests that a tripeptide is sufficiently long as a ligand. On the basis of these results, the mode of substrate binding of trypsin is discussed.

Image emission platelet laser for optical information processing

A laser light image corresponding to an image of an input transparency projected by a Rhodamine-6G dye laser has been emitted from an ultrathin GaAs crystal wafer. The image emission laser can be used as a new active device for optical parallel processings. Experimental results of image thresholding and wavelength converting are presented.