Phorbol ester and okadaic acid-resistant cells: the crossroads of signal transduction and drug resistance

Many factors are involved in the development of drug resistance for anticancer drugs. The drugs should pharmacokinetically attain the appropriate concentration. They should be metabolized to the active forms. Tumor cells should have sensitivity to them. Several molecular and biochemical mechanisms that may explain cellular drug resistance have been identified. The contribution of protein phosphorylation and dephosphorylation for drug resistance is demonstrated in phorbol ester and okadaic-acid-resistant cells. The modulation of drug resistance by substances that affect the signal transduction pathway is an important issue in the development of an effective method for overcoming drug resistance.

CD40 signaling-mediated induction of Bcl-XL, Cdk4, and Cdk6. Implication of their cooperation in selective B cell growth

Signals sent through CD40 play crucial roles in B cell differentiation, including blocking apoptosis of germinal center B cells. In this study, using a murine B cell WEHI-231 line that undergoes apoptosis by the cross-linking of surface Ag receptors (sIgM), we have demonstrated that CD40 signalings are linked to induction of the Bcl-xL, Cdk4, and Cdk6 proteins whose expression was significantly suppressed by the apoptotic signal through sIgM. Mutational analyses of CD40 revealed that the domain of human CD40 required for blocking apoptosis of WEHI-231 cells coincides with that required for Bcl-xL induction. Signals through sIgM arrest cells in the G1 phase of the cell cycle, which is followed by apoptosis. However, while constitutive expression of Bcl-XL leads to the inhibition of apoptosis. Nevertheless, Bcl-xL fails to induce S phase entry. By CD40 signalings, both Cdk4 and Cdk6 resume their normal expression levels, which are sufficient for passing the restriction point in G1 even in the presence of the apoptotic signals mediated by sIgM. These results suggest that cooperation of Bcl-xL, Cdk4, and Cdk6 induced by CD40 signaling plays a key role in CD40-mediated selective growth of B cells.

CD40 signaling-mediated induction of Bcl-XL, Cdk4, and Cdk6. Implication of their cooperation in selective B cell growth

Signals sent through CD40 play crucial roles in B cell differentiation, including blocking apoptosis of germinal center B cells. In this study, using a murine B cell WEHI-231 line that undergoes apoptosis by the cross-linking of surface Ag receptors (sIgM), we have demonstrated that CD40 signalings are linked to induction of the Bcl-xL, Cdk4, and Cdk6 proteins whose expression was significantly suppressed by the apoptotic signal through sIgM. Mutational analyses of CD40 revealed that the domain of human CD40 required for blocking apoptosis of WEHI-231 cells coincides with that required for Bcl-xL induction. Signals through sIgM arrest cells in the G1 phase of the cell cycle, which is followed by apoptosis. However, while constitutive expression of Bcl-XL leads to the inhibition of apoptosis. Nevertheless, Bcl-xL fails to induce S phase entry. By CD40 signalings, both Cdk4 and Cdk6 resume their normal expression levels, which are sufficient for passing the restriction point in G1 even in the presence of the apoptotic signals mediated by sIgM. These results suggest that cooperation of Bcl-xL, Cdk4, and Cdk6 induced by CD40 signaling plays a key role in CD40-mediated selective growth of B cells.

Dystrophic form of inherited epidermolysis bullosa in a dog (Akita Inu)

We report a dog with dystrophic epidermolysis bullosa. This 4-year-old female Akita Inu, a species of Canis familiaris var. japonicus Temminck, had a 3-year-history of ulcers and scars over the pressure areas on the limbs, and dystrophic nails, since the age of 1 year, which corresponds to early adulthood in humans. Electron microscopy of a blister revealed separation beneath the lamina densa, and a reduction in the number of anchoring fibrils. The NC-1 domain of type VII collagen was positively stained with monoclonal antibody LH7.2 at the basement membrane zone. These findings indicate that humans and dogs have a similar response to antibody LH7.2, which may aid the development of an animal model for this disease.

Angiotensin II activates pp60c-src in vascular smooth muscle cells

The angiotensin II type-1 (AT1) receptor, a G protein-coupled receptor, lacks intrinsic kinase activity. However, recent data show that angiotensin II (Ang II) stimulates tyrosine phosphorylation of phospholipase C-gamma 1 (PLC-gamma 1), Stat91 (one of the signal transducers and activators of transcription), and paxillin in vascular smooth muscle cells. The tyrosine kinases responsible for these phosphorylation events are unknown. Src family kinases have been shown to phosphorylate PLC-gamma 1 and to be activated by G protein-coupled receptors. We hypothesized that pp60c-src associates with the AT1 receptor and is activated after Ang II stimulation of smooth muscle cells. We immunoprecipitated pp60c-src from Ang II-stimulated vascular smooth muscle cells and measured pp60c-src activity by autophosphorylation and by phosphorylation of enolase. Both assays demonstrated an approximately threefold increase in pp60c-src activity within 1 minute. A similar increase in Ang II-stimulated pp60c-src activity was observed in Chinese hamster ovary cells transfected with the AT1 receptor but not in untransfected cells. These data are the first to show that pp60c-src is activated by Ang II. To determine if pp60c-src associated with the AT1 receptor, the AT1 receptor was immunoprecipitated (with two different antibodies), and Western blots were performed with two different anti-pp60c-src antibodies. No pp60c-src was detected. In addition, direct interaction between the AT1 receptor and pp60c-src could not be demonstrated by using a glutathione S-transferase (GST)-AT1 fusion protein to bind proteins from cell lysates stimulated by Ang II.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypotensive effects of a new transdermal delivery system for clonidine (M-5041T) in spontaneously and renal hypertensive rats

1. Antihypertensive effects of a new transdermal delivery system for clonidine (clonidine tape; M-50417) were investigated in spontaneously hypertensive rats (SHR), 2-kidney, 1-clip renal hypertensive rats (RHR) and deoxycorticosterone acetate/salt (DOCA/Salt) hypertensive rats. 2. M-5041T (0.5-4.5 mg/kg) elicited long-lasting hypotensive effects and bradycardia in a dose-dependent manner during 24 h patching in three hypertensive models compared with oral clonidine (100 mu g/kg). 3. The most hypotensive effect of M-5041T was observed in DOCA/salt hypertensive rats. 4. Co-administration of M-5041T with either trichloromethiazide (1 mg/kg, orally) or nifedipine (3 mg/kg, orally) at each dose without hypotensive effects per se induced significant hypotension in SHR. 5. Repeated administrations of M-5041T (1.5 mg/kg per day) for a consecutive 7 days produced significant hypotensive effects at postpatching 6 h, and recovered a postpatching 24 h in SHR. 6. Repetitive M-5041T administrations displayed no tolerance on the hypotensive effects and were devoid of any withdrawal syndrome. 7. These findings suggest that M-5041T may serve as an efficiently useful antihypertensive transdermal delivery system in humans.

Enhanced interaction between tubulin and microtubule-associated protein 2 via inhibition of MAP kinase and CDC2 kinase by paclitaxel

Paclitaxel, an anti-mitotic anti-cancer agent, is active against solid tumors. The inhibition of depolymerization and promotion of microtubular assembly are essential for the anti-tumor activity of paclitaxel. Microtubule-associated proteins (MAPs) co-polymerize with tubulin and play some roles in microtubular dynamics. We examined the effect of paclitaxel on the interaction between tubulin and MAPs. Human lung-cancer cells, PC-14, were synchronized to G1/S border by the thymidine-double-block technique. After release from exposure to thymidine, the cells were treated briefly with 2 nM paclitaxel and the levels of alpha and beta tubulins and MAPs were examined after various times. Immunoblot analysis of paclitaxel-treated cells showed no changes in the overall expression of alpha and beta tubulins, microtubule-associated protein 2 (MAP2) or MAPs in comparison with controls. The samples were immunoprecipitated with anti-alpha- and anti-beta-tubulin antibodies and reblotted with an anti-MAP2 antibody, which showed that the amount of co-immuno-precipitated MAP2 in the synchronized cells, were increased by the brief paclitaxel treatment. These results suggest that paclitaxel treatment enhances the interaction between alpha and beta tubulins and MAP2. Since the phosphorylation state of MAP2 regulates the affinity of MAP2 for tubulins, and mitogen-activated protein (MAP) kinase is considered to be one of the kinases responsible for MAP2 phosphorylation, the effect of paclitaxel treatment on the MAP-kinase activity of synchronized PC-14 cells was examined. Two bands with molecular masses of 42 and 44 kDa were detected by an "intra-gel" MAP-kinase assay using myelin basic protein as the substrate. Paclitaxel treatment inhibited the MAP-kinase activity of PC-14 cells and inhibition was maximal at the G2/M phase of the cell cycle. Similar, concentration-dependent inhibition by paclitaxel of cellular MAP kinase of human synchronized small-cell lung carcinoma, H69, was observed. No inhibition of the MAP kinase of the paclitaxel-resistant sub-line H69/Txl by paclitaxel was observed, suggesting that some change of the MAP-kinase cascade had occurred in these cells. No direct inhibition of MAP-kinase activity by paclitaxel was observed in the cell-free assay (in vitro), suggesting that paclitaxel did not inhibit MAP kinase directly. Since it has been speculated that p34cdc2 kinase is also a kinase that phosphorylates MAP2, the effect of paclitaxel treatment on the p34cdc2-kinase activity of synchronized PC-14 and PC-9 cells was examined. Paclitaxel inhibited p34cdc2-kinase activation at the G2/M phase. These results suggest that paclitaxel inhibited MAP kinase and p34cdc2 kinase in vivo indirectly. These actions of paclitaxel may be responsible for the increased affinity between MAP2 and tubulins that it induces.

Gamma-glutamylcysteine synthetase gene overexpression results in increased activity of the ATP-dependent glutathione S-conjugate export pump and cisplatin resistance

The ATP-dependent glutathione S-conjugate export pump (GS-X pump) has been suggested to play a role in the mechanism of cisplatin resistance. The purpose of this study was to determine the relationship between intracellular glutathione (GSH) levels and GS-X pump activity and whether GS-X pump overexpression results in cisplatin resistance. We transfected the human gamma-glutamylcysteine synthetase (gamma-GCS) gene into a human small-cell lung cancer cell line, SBC-3, producing SBC-3/GCS. The intracellular GSH content of SBC-3/GCS was twice that of the parental line, its GS-X pump activity was significantly enhanced and cellular cisplatin accumulation decreased. SBC-3/GCS showed higher resistance (relative resistance value of 7.4) to cisplatin than the parental line SBC-3. These data indicate that gamma-GCS gene overexpression induces cellular cisplatin resistance associated with increases in both the GSH content and GS-X pump activity, resulting in reduced cisplatin accumulation. In conclusion, GS-X pump expression is related to cellular GSH metabolism and involved in cisplatin resistance.

Dietary salt decreases cytosolic calcium in platelets from Dahl salt-sensitive rats

To determine whether abnormal cellular Ca2+ handling is involved in salt-induced hypertension of Dahl salt-sensitive rats (DS), we investigated Ca2+ handling in fura 2-loaded platelets of DS and Dahl salt-resistant rats (DR) fed a high-NaCl (8%) or a low-NacL (0.3%) diet for 4 wk from 5 wk of age. At 5 wk of age, blood pressure, resting cytosolic Ca2+ concentration ([Ca2+]i), the thrombin-evoked increase in [Ca2+]i and the size of internal Ca2+ stores of DS were comparable with those of DR. After 4 wk on the diets, resting [Ca2+]i of DS on high-NaCl diet was lower than that of DS on low-NaCl diet, and there was no effect of high salt intake on resting [Ca2+]i in DR. In DS, high salt intake attenuated the [Ca2+]i response to thrombin in the presence of external Ca2+. In contrast, the [Ca2+]i response to thrombin in the absence of external Ca2+ was enhanced by high salt intake in DS. The size of internal Ca2+ stores was increased by high salt intake in DS but not in DR. These data suggest that it is not obligatory for hypertension to be accompanied by an increase in platelet [Ca2+]i.

Chimeric TLS/FUS-CHOP gene expression and the heterogeneity of its junction in human myxoid and round cell liposarcoma

Myxoid liposarcomas have a unique and specific t(12;16)q13;p11) chromosomal translocation. The breakpoint has recently been identified and shown to involve the TLS/FUS gene on chromosome 16 and the CHOP gene on chromosome 12. This translocation causes fusion of these genes resulting in the expression of a novel chimeric TLS/FUS-CHOP message. Using the polymerase chain reaction with primer sets derived from sequences of TLS/FUS and CHOP cDNAs, we could amplify three types of the fusion transcripts from seven of seven samples of myxoid and round cell liposarcomas. In six of the seven positive samples, two kinds of chimeric messenger RNAs were found that have been reported previously. However, the last sample had a novel chimeric message that had an extra sequence of 33 bp derived from the TLS/FUS gene. Thus, it was shown that these fusion transcripts had a varying extent of the sequence of TLS/FUS gene incorporated at the site of the fusion. However, the TLS/FUS-CHOP fusion transcripts were not detected in two pleomorphic liposarcomas or in three myxoid variants of malignant fibrous histiocytomas. Our findings indicate that in liposarcomas TLS/FUS-CHOP fusion transcripts have variations at the junction of chimeric messages, which was the case for Ewing's sarcoma. Detection of the chimeric message by reverse transcription polymerase chain reaction was also suggested to be a useful approach for the diagnosis of myxoid and round cell liposarcomas that have (12;16) translocation, and for distinguishing them from pleomorphic liposarcoma and myxoid variant of malignant fibrous histiocytomas.

Unique binding of a novel synthetic inhibitor, N-[3-[4-[4-(amidinophenoxy)carbonyl]phenyl]-2-methyl-2-propenoyl]- N-allylglycine methanesulfonate, to bovine trypsin, revealed by the crystal structure of the complex

Trypsin and N-[3-[4-[4-(amidinophenoxy)carbonyl]phenyl]-2-methyl-2-propenoyl]- N-allylglycine methanesulfonate (1), a newly designed and orally active synthetic trypsin inhibitor, were cocrystallized. The space group of the crystal is P2(1)2(1)2(1) with cell constants a = 63.74 A, b = 63.08 A, and c = 69.38 A, which is nearly identical to that of the orthorhombic crystal of guanidinobenzoyltrypsin. The structure was refined to a crystallographic residual R = 0.176. The refined model of the 1-trypsin complex provides the structural basis for the reaction mechanism of 1. On the basis of the present X-ray results, it is proposed that the potent inhibitory activity of 1 is mainly due to the formation of an acylated trypsin through an "inverse substrate mechanism" and its low rate of deacylation.

Video-assisted thoracoscopic surgery of bullous and bleb disorders of the lung using endoscopic stapling device

The video-assisted thoracic surgical (VATS) approach appears to be a viable alternative to thoracotomy when surgical management of bullous and bleb disorders of the lung is required. Fifty patients with giant bullae (n = 6) and spontaneous pneumothoraces (n = 44) were recently treated by our group using the VATS approach and endoscopic stapling devices. Of the 50 patients, 47 were managed completely by the VATS approach, including six giant bullae that were asymptomatic in five and infectious in one and 41 pneumothoraces, of which 16 were first episode and 25 with recurrent pneumothorax. Median operating times for the bullous and bleb excisions were 147.8 and 45.9 min, respectively (p < 0.01), and median chest tube durations were 5.2 and 1.2 days, respectively (p < 0.05). There was no mortality, and significant morbidity was limited to prolonged air leak in more than 5 days in three patients and postoperative atelectasis in two patients. Median hospital stays of patients with bullous excision was 11.3 days compared with 4.7 days of those with bleb excision. We conclude that the VATS treatment is a safe, effective procedure in patients with bullous and bleb disorders of the lung even in asymptomatic giant bullae or spontaneous pneumothoraces with the first episode. The advantages of the VATS approach for these diseases are ease of operation, less pain, early mobility, and superior cosmetic results.

Binding specificity of mutagenic tryptophan pyrolysates for DNA conformation: spectroscopic and viscometric studies

The compounds, 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), are major potent mutacarcinogens isolated from tryptophan pyrolysate. In order to investigate their interaction with DNA and effects on DNA conformation, studies involving circular dichroism, fluorescence and absorption spectroscopy and viscometric titration were performed. The results show that (a) Trp-P-1 and Trp-P-2 are potent intercalators of DNA with nearly the same specificity for the A-T and G-C (alternative purine-pyrimidine) base sequences, (b) the interaction of Trp-P-1 with the B-form of DNA is biphasic so that stiffening of the B-DNA conformation occurs over the range r ([Trp-P-1]/[DNA]) = 0-2.5, followed by transformation of B to the non-B conformation at r > 2.5, (c) the transformation to the non-B structure is not observed for Trp-P-2, although stiffening of the B-DNA conformation similarly occurs, and (d) both Trp-P-1 and Trp-P-2 promote unwinding of the salt-induced Z-DNA to give the B-form. These data indicate that the noncovalent interaction of Trp-P with DNA is mainly dependent on the B-form conformation.

Superoxide anions in the pathogenesis of talc-induced cerebral vasocontraction

We have recently reported that sustained contraction of the canine basilar artery induced by the intrathecal injection of talc (crystallized hydrous magnesium silicate) mimicked delayed vasospasm following subarachnoid haemorrhage. The present study aims to examine the pathomechanism underlying talc-induced vasocontraction, from the viewpoint of free radical theory, which has been established as a cause of delayed vasospasm. We estimated the effects of a prolonged intrathecal infusion of human recombinant Cu/Zn superoxide dismutase (hr SOD) on the contraction of the basilar artery caused by the intrathecal injection of talc in beagle dogs, which were assigned to the three groups: G1, sham operation with saline treatment; G2, talc injection with saline treatment; and G3, talc injection with 2 ml of hr SOD (7 x 10(4) U/ml) treatment. Talc administration resulted in the reduction in the angiographic calibre of the basilar artery by 63 and 61% on days 3 and 7 (G2). The treatment with hr SOD (G3) led to a significant attenuation of talc-induced contraction of the basilar artery on days 3 (P < 0.05 vs. G2) and 7 (P < 0.05 vs. G2). In the basilar artery wall of days 3 and 7 in G2, pathological changes such as myonecrosis, cytoplasmic vacuolation and detached intercellular junctions were observed. However, these pathological changes almost disappeared in G3. The present findings suggest that superoxide anions may initiate and/or mediate talc-induced vasocontraction and subsequent structural damage of the basilar artery.

Suppression of episodic growth hormone secretion in streptozotocin-induced diabetic mice: time-course studies on the hypothalamic pituitary axis

To elucidate the roles of the hypothalamic peptides, GH-releasing hormone (GRH) and somatostatin (SRIH), potentially responsible for altered GH dynamics in diabetes, we studied the time courses of their changes in level associated with altered GH secretion in streptozotocin (STZ)-induced diabetic mice. Diabetic mice were used at 4, 7, and 14 days after STZ injection for analyses of 1) GH secretion in vivo, 2) hypothalamic GRH and SRIH messenger RNA (mRNA) levels, 3) pituitary GH mRNA and protein contents, and 4) pituitary GH response to GRH in vitro. GH secretion was completely suppressed 7 and 14 days after STZ injection. The hypothalamic GRH mRNA level was reduced to 59.8%, 61.2%, and 48.5% of control values at 4, 7, and 14 days, respectively. In contrast, the hypothalamic SRIH mRNA level was not altered at all of these time points. Pituitary GH mRNA and protein contents were significantly reduced to 70.2% and 61.5% of those in controls, respectively, only at 14 days. Pituitary GH responses to GRH at three doses (10, 50, and 250 nM) in vitro were remarkably increased at 4, 7, and 14 days. These findings indicate that the diabetic state rapidly and primarily inhibits hypothalamic GRH gene expression without affecting SRIH. A persistent decrease in hypothalamic GRH tone has been suggested to result in inhibition of GH synthesis in the pituitary. Enhancement of GH responsiveness to GRH may be due to the up-regulation of GRH receptors in the pituitary.

Selection of absorption lines for I(2)-planar laser-induced fluorescence measurement of temperature in a compressible flow

It is very important for I(2)-planar laser-induced fluorescence measurement of temperature in a compressible flow to choose a pair of absorption lines appropriate to the temperature range. The method for selection of suitable pairs of absorption lines of I(2) in the transition of B(3)II(ou) + (ν' = 43) ? X(1)Σ(g) + (ν" = 0)is described. By the use of many pairs of absorption lines, the temperature dependence of the ratio between the fluorescence signals is calculated theoretically and is also investigated in experiments in which several pairs are applied to determination of the temperature distribution of a supersonic free jet.

Inhibitory effects of interleukin-1 on growth hormone secretion in conscious male rats

Although various pathophysiological effects of interleukin (IL) on the CRF-ACTH-adrenal axis and gonadotropin secretion have been studied extensively, the effects of IL on GH secretion still remain to be elucidated. We investigated the possible effects of IL on GH secretion in six groups of conscious rats. In four groups, IL was administered by continuous iv infusion and in the other two, by intracerebroventricular injection. Saline-treated rats served as controls for these groups. Sequential blood sampling was performed every 20 min in all groups, and the plasma GH concentration was determined by RIA. The expression of hypothalamic c-fos protein in a separate group was examined by immunohistochemistry. Continuous infusion of both IL-1 alpha and IL-1 beta (10 ng/min) significantly inhibited GH surges. The plasma IL-1 level was elevated to 2-3 ng/ml. Continuous iv infusion of IL-2 and IL-6 had no effect on GH secretion. The intracerebroventricular injection of both IL-1 alpha and IL-1 beta significantly inhibited GH surges, and the inhibitory effect was much greater for IL-1 beta than for IL-1 alpha. Continuous iv infusion of IL-1 beta markedly stimulated c-fos expression in specific hypothalamic nuclei, particularly in the paraventricular nucleus. These findings suggest that, in the rat, IL-1 inhibits GH secretion through its peripheral and central actions.

Gene expression of hypothalamic growth hormone (GH)-releasing hormone and somatostatin does not correlate with pulsatile secretion of GH in the adult mouse

The secretion of growth hormone (GH) shows a pulsatile pattern in many mammalian species, and depends on the interaction of two hypothalamic hormones, GH-releasing hormone (GHRH) and somatostatin (SRIH). A surge of GHRH secretion into the hypophysial portal blood induces peak secretion of GH from the anterior pituitary. To study whether the rhythmic and reciprocal oscillation in secretion of GHRH and SRIH are associated with changes in synthesis of these peptides, we examined the expression of hypothalamic GHRH and SRIH mRNA by Northern blotting during trough and peak phases of GH secretion in male mice. Hypothalamic GHRH and SRIH mRNA levels did not differ between trough and peak phases of GH secretion. This result suggests that changes in GHRH and SRIH secretion have little association with changes in the synthesis of these peptides at the hypothalamus in the male mouse.

(S)-C alpha-ethyl, C alpha-benzylglycine [(S)-(alpha Et)Phe] peptides fold in left-handed helical structures

The first x-ray diffraction structure analysis of a C alpha-ethyl, C alpha-benzylglycine [(alpha Et)Phe]-containing peptide, N alpha-benzyloxycarbonyl-alpha-aminoisobutyryl-alpha-amino-isobutyr yl-(S)- C alpha-benzylglycyl-alpha-aminoisobutyric acid (methanol solvate), has been performed. In the crystal state the N alpha-protected tetrapeptide is folded in an incipient, left-handed 3(10)-helical structure. This finding confirms that the relationship between (alpha Et)Phe alpha-carbon chirality and screw sense of the helix that is formed is opposite to that exhibited by protein amino acids, including Phe.

Enhancement of aromatic amino acid-nucleic acid base stacking interaction by metal coordination to base: fluorescence study on a tryptophan-Pt(II)-guanine ternary complex

In order to investigate the effect of the Pt(II) ion on the stacking interaction between tryptophan and a guanine base, the quenching of Trp fluorescence was monitored for some systems in the absence and presence of the metal ion, and the association constants were obtained by the analysis of Eadie-Hofstee plots. All spectral data suggested that the stacking interaction is enhanced by the Pt(II) coordination to the guanine N7 atom. The result indicates the importance of the metal ion as a bookmark in the specific recognition of a nucleic acid base by an aromatic amino acid residue.

Design of noncovalent trypsin inhibitor based on the X-ray crystal structure of the complex

The inhibitory mechanism of trans-4-aminomethylcyclohexanecarbonyl-L-phenyl-alanine-4-carbo xymethylanilide (1), a noncovalent serine protease inhibitor synthesized based on previous structure-activity studies, was clarified based on the X-ray crystal structure of the complex (2.2 A resolution, R = 0.175), where the amino group of the aminomethylcyclohexane moiety was bifurcately hydrogen-bonded to the carboxyl oxygens of Asp 189 side group (specificity pocket), and the hydrogen bonds of the cyclohexanecarbonyl oxygen to NHs of Gly 193 and Ser 195 residues (oxyanion hole) and of Phe NH to Ser 195 O gamma atom (catalytic triad) were observed. In contrast, the Phe benzene moiety and terminal carboxymethylanilide of 1 were not well located on the electron density map, suggesting the conformational freedom of these P1' and P2' sites at the binding pocket. Based on these insights, trans-4-aminomethylcyclohexanecarbonyl-4-nitro-L-phenylalanine-4-+ ++benzoylanilide (2) was designed, in which the P1' and P2' sites were modified so as to effectively interact with the amino acid residues of trypsin binding pocket via hydrogen bonding and van der Waals interactions, respectively. Consequently, 2 showed 40 times higher inhibitory activity against trypsin than 1.