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The phosphoenolpyruvate carboxylase (PEPC) isozyme involved in C4 photosynthesis is known to undergo reversible regulatory phosphorylation under illuminated conditions, thereby decreasing the enzyme's sensitivity to its feedback inhibitor, L-malate. For the direct assay of this phosphorylation in intact maize leaves, phosphorylation state-specific antibodies to the C4-form PEPC were prepared. The antibodies were raised in rabbits against a synthetic phosphorylated 15-mer peptide with a sequence corresponding to that flanking the specific site of regulatory phosphorylation (Ser15) and subsequently purified by affinity-chromatography. Specificity of the resulting antibodies to the C4-form PEPC phosphorylated at Ser15 was established on the basis of several criteria. The antibodies did not react with the recombinant root-form of maize PEPC phosphorylated in vitro. By the use of these antibodies, the changes in PEPC phosphorylation state were semi-quantitatively monitored under several physiological conditions. When the changes in PEPC phosphorylation were monitored during the entire day with mature (13-week-old) maize plants grown in the field, phosphorylation started before dawn, reached a maximum by mid-morning, and then decreased before sunset. At midnight dephosphorylation was almost complete. The results suggest that the regulatory phosphorylation of C4-form PEPC in mature maize plants is controlled not only by a light signal but also by some other metabolic signal(s). Under nitrogen-limited conditions the phosphorylation was enhanced even though the level of PEPC protein was decreased. Thus there seems to be some compensatory regulatory mechanism for the phosphorylation.

A spider toxin NSTX-3 obtained from the venom of Papua New Guinean spider, Nephila maculata was synthesized in order to confirm its proposed structure and to supply the sample for the biological tests. The structure of NSTX-3 is now established as 2,4-dihydroxyphenylacetyl-L-Asn→Cad←Pua←L-Arg, where Cad stands for cadaverine and Pua for putreanine.

The isomers of sialic acid with 6-acetylamino group, 1a and 1b were synthesized from furanose 3a and 3b respectively obtained by aldol condensation of D -glucose with oxalacetic acid.

A main component of ganglioside M5 from egg of the sea urchin, Anthocidaris crassispina, Neu5Gcα2 → 6Glcβ1 → 1Cer (1), which has N-glycolyl group in neuraminic acid part, as well as phytosphingosine and saturated nonhydroxy fatty acid in ceramide part was first synthesized starting from N-acetylneuraminic acid.

Clavamine, a new insecticidal toxin isolated from the venom of Joro spider (Nephila clavata) was totally synthesized in order to confirm the proposed structure. In clavamine, a fragment of glycylalanine is inserted in the structure of NSTX-3, a New Guinean spider toxin. The synthesis determined the chemical structure of clavamine unambiguously.

In a study on structure-activity relationship of spider toxin NSTX-3 obtained from venom of Nephila maculata, nine analogs or fragments of natural toxin were synthesized. Among them, des-Arg- NSTX-3 was found to be the minimum structure for blocking the excitatory transmission in the crustacean neuromuscular synapse. A positive charge of the arginine part was concluded to play the most important role for exhibition of the activity.

In the previous paper [Eur. J. Biochem. 124, 405 (1982)], we demonstrated that chemically synthesized lipid-A analogues such as the 1-monophosphate or 1,4'-diphosphate of 6-O-(2-deoxy-2-tetradecanoylamino-6-O-tetradecanoyl-D-glucopyra nos yl)-2-deoxy-2-tetradecanolyamino-3,4-di-O-tetradecanoyl-D-gluco pyr anose enhanced immunogenicity of liposomal model membranes sensitized with amphipathic antigen when they were incorporated in the same liposomes. Here we extend the observation by testing the recently synthesized analogues including diglucosamine analogues carrying hydroxy and acyloxy fatty acids. Among the analogues tested, those which showed higher adjuvant and mitogenic activities in the liposomal system were N-acylated and O-acylated beta-1,6-linked D-glucosamine disaccharides carrying either amide-bound 3-hydroxytetradecanoic acids in addition to phosphate in position 1 of the reducing sugar or amide-bound 3-tetradecanoyloxytetradecanoic acids. The analogue carrying both amide-bound 3-hydroxytetradecanoic acids and phosphate in position 4 of the non-reducing sugar showed weak adjuvant activity and marginal mitogenic activity.

The effects of polyclonal B cell activation (PBA) of cell walls and their cell wall fractions obtained from several kinds of gram-positive bacteria were studied using the anti-sheep red blood cell (SRBC) or anti-trinitrophenylated (TNP) SRBC plaque forming cell (PFC) responses of cultured spleen cells from Balb/c, athymic nu/nu, their littermates (nu/+), C3H/He (LPS-responder), C3H/HeJ (LPS-non-responder), (CBA/N × Balb/c) F1 male with an X-linked defect in B cell function and the F1 female mice. The cell walls of Staphylococcus epidermidis (ATCC 155), Lactobacillus plantarum (ATCC 8014), Micrococcus lysodeikticus (NCTC 2665), Mycobacterium rhodochrous (ATCC 184), Streptomyces gardneri (ATCC 23911) and Nocardia corynebacteriodes (ATCC 14898) had the ability to induce polyclonal B cell responses in the spleen cells of Balb/c, nu/nu, nu/+, C3H/He and C3H/HeJ mice. The cell wall fractions prepared by enzymatic digestion from the cell walls of S. epidermidis, S. gardneri or N. corynebacteriodes were also capable of inducing polyclonal B cell responses. The responses of spleen cells from (CBA/N × Balb/c) F1 male mice to these active preparations, except the cell walls of M. rhodochrous, were much lower than those of the F1 female mice. These findings indicate that the majority of the cell wall preparations lacks PBA ability for spleen cells with the CBA/N defect, except for the cell walls of M. rhodochrous which possess this ability. The PBA-ability of synthetic peptidoglycan, muramyl dipeptide (N-acetylmuramyl-L-alanyl-D-isoglutamine, MDP), was also examined, and a similar activity was observed in MDP.

A pentaacyl precursor of lipid A biosynthesis, termed precursor Ib, and a structural isomer have been chemically synthesized. These compounds were, in comparison to synthetic Escherichia-coli type lipid A or lipopolysaccharide, analyzed for their activity in typical endotoxin test systems. It was found that both precursor Ib and the isomer exhibited similar or only slightly lower pyrogenic, lethal and Shwartzman-phenomenon-inducing activity than lipid A. All preparations were comparable in their B-lymphocyte mitogenicity, macrophage-activating capacity and immunoreactivity towards lipid A antisera. The proton nuclear magnetic resonance spectra of the 1-dephospho derivative of synthetic and bacterial precursor Ib were indistinguishable proving that the previously proposed structure for precursor Ib is correct.

The binding of 14C-labelled tuberactinomycin O was analysed in equilibrium dialysis cells. The ionic conditions and the concentration of the labelled drug used in the binding assays allowed the binding of just one drug molecule per non-programmed ribosome. Under these conditions, the occupation of the ribosomal P-site by deacylated tRNAPhe in the presence of poly(U) increased the amount of [14C]tuberactinomycin O bound by a factor of two. Kanamycin, gentamicin and neomycin reduced the binding of tuberactinomycin O, whereas chloramphenicol, tetracycline, streptomycin and puromycin had no effect. A stimulation of the binding of tuberactinomycin O was found upon addition of erythromycin.

A synthetic lipid A (preparation 516), containing seven acyl groups and representing one component of natural free lipid A of Salmonella minnesota R595, has been investigated for biological activity in a number of endotoxin test systems. It was found that the synthetic preparation was, in typical in vivo endotoxin tests (lethality, pyrogenicity, Shwartzman reactivity) as well as in its antigenicity and macrophage activation capacity, significantly less active than natural Salmonella lipid A. However, in other in vitro assay systems (B-cell mitogenicity, complement activation, Limulus amoebocyte lysate gelation) it expressed similar activity as Salmonella lipid A.

Interferon-inducing, pyrogenic and proclotting enzyme of horseshoe crab activation activities of chemically synthesized lipid A analogues were investigated and compared with the same activities of a natural lipid A. These analogues are nonphosphorylated, C-1 or C-4′ monophosphorylated and C-1,4′ bisphosphorylated derivatives of β-1,6-linked d-glucosamine disaccharide possessing both ester-bound and amide-bound fatty acid substituents. Fatty acid substituents of the analogues are tetradecanoyl (C14), (R)-3-hydroxytetradecanoyl (C14-OH) or (R)-3-tetradecanoyloxytetradecanoyl [C14-O-(C14)] groups. The biological activities of the samples were assayed after solubilization with triethylamine and complexing with bovine serum albumin. Interferon-inducing activity was exhibited by both the C-1 monophosphorylated compounds examined. Ester-bound and amide-bound fatty acid substituents of these compounds are both C14 or C14 and C14-OH, respectively. Nonphosphorylated, C-4′ monophosphorylated and C-1,4′ bisphosphorylated compounds possessing the same fatty acid substituents as those of the C-1 monophosphorylated compounds showed no detectable interferon-inducing activity. C-4′ monophosphorylated compounds possessing C14-OH as ester-bound and C14-OH or C14-O-(C14) as amide-bound fatty acid substituents exhibited interferon-inducing activity, but nonphosphorylated compounds possessing the same fatty acid substituents did not. None of the analogues exhibited significant pyrogenicity nor proclotting enzyme of horseshoe crab activation activity under the conditions employed in this study.

Synthetic lipid A part structures corresponding structurally to a biosynthetic lipid A disaccharide precursor have been analyzed for endotoxic activity in several systems in vivo and in vitro. It was found that a synthetic beta-1,6-linked D-glucosamine disaccharide, which carries four molar equivalents of (R)-3-hydroxytetradecanoyl residues in positions 2, 3, 2' and 3' and phosphoryl groups in positions 1 and 4' (preparation 406), exhibited lethal toxicity, B lymphocyte mitogenicity, the capacity to engender prostaglandin formation in macrophages and to induce endotoxic tolerance, as well as serological lipid A antigenicity. On a weight basis, preparation 406 was of comparable activity to lipid A precursor and bacterial free lipid A. Preparation 406, like lipid A precursor, lacked, however, the ability to induce the local Shwartzman phenomenon and both preparations were of moderate pyrogenicity. Two further synthetic analogues which contained only one phosphoryl group (preparation 404 at C-4', preparation 405 at C-1) showed comparable or diminished activity depending on the test system employed, except in the capacity to inactivate complement where they exhibited, in contrast to preparation 406, significant activity. The results show that the endotoxic principle of lipopolysaccharides, as postulated previously is embedded in the lipid A component. Our results also suggest initial conclusions on the structural requirements for the expression of endotoxin activities.

We report progress in elucidating the structure of nisin, a naturally occurring peptide antibiotic. Nisin contains five rings constrained by lanthionine or methyllanthionine bridges, as well as alpha, beta-unsaturated amino acids. We have determined conformations for two model compounds of ring A and a derivative of ring B through interactive nmr and computer simulation studies. High-resolution nmr techniques provides structural information, which was further refined through molecular dynamics simulations. These methods are being applied to the remaining constrained fragments of the molecule. This conformational information will be employed in an aufbau approach to determining the structure of the entire molecule.

The structure/activity relationship of lipid A, a bioactive center of endotoxic lipopolysaccharides, in the activation of the clotting enzyme cascade of a horseshoe crab amoebocyte lysate (Limulus activity) and the complement system in human serum, was examined using synthetic lipids A and related compounds. Regarding Limulus activity, a newly developed colorimetric method, which utilizes a mixture of recombined clotting factors and a chromogenic substance, was much more sensitive for detecting changes in the chemical structure of test compounds than the conventional gelation method using the amoebocyte whole lysate. (beta 1-6)-D-Glucosamine disaccharide bisphosphates, which had neither 3-hydroxyacyl nor 3-acyloxyacyl groups, and acylglucosamine phosphates, which in structure correspond or are analogous to the non-reducing or reducing moieties of lipids A and biosynthetic disaccharide lipid A precursors showed only negligible activity in the colorimetric tests, but they exhibited a distinct though much weaker gelation activity than the parent disaccharide molecules. The assay results obtained by the colorimetric Limulus test correlate better with the pyrogenicity of the test synthetic compounds than those given by the gelation method, although the dependence of pyrogenicity on chemical structure is greater. The presence of 3-hydroxyacyl groups on the bisphosphorylated (beta 1-6)-D-glucosamine disaccharide backbone is the prerequisite for effective activation of the clotting enzyme cascade of horseshoe crab amoebocyte lysate, while the presence of an adequate number (one or two) of 3-acyloxyacyl groups on the disaccharide bisphosphate backbone is needed for full pyrogenicity. Complement activation, on the other hand, showed structural requirements quite different from those for the colorimetric Limulus activity and the pyrogenicity. The disaccharide compounds that had only non-hydroxylated acyl groups, acylated glucosamine phosphates that had the structure of the non-reducing portion of lipids A and biosynthetic disaccharide precursors, which were scarcely active in the colorimetric Limulus test, caused complement activation comparable to or sometimes stronger than that of the parent disaccharide molecules. Acylglucosamine phosphates, corresponding in structure to the reducing moiety of disaccharide compounds, however, showed little activity.

An intracellular clotting factor, factor C, found in the horseshoe crab hemocytes is a lipopolysaccharide-sensitive serine-protease zymogen, which participates in the initiation of the hemolymph clotting system [T. Nakamura et al. (1986) Eur. J. Biochem. 154, 511-521]. The subsequent study of this zymogen, using various synthetic lipid A analogues, revealed that the zymogen factor C is rapidly activated by acylated (beta 1-6)-D-glucosamine disaccharide bisphosphate (synthetic Escherichia coli-type lipid A), and the corresponding 4'-monophosphate analogues. However, the corresponding non-phosphorylated lipid A did not activate factor C, indicating that a phosphate ester group linked with the (beta 1-6)-D-glucosamine disaccharide backbone is required for the zymogen activation. During these studies we also found that the zymogen factor C is significantly activated by acidic phospholipids, such as phosphatidylinositol, phosphatidylglycerol and cardiolipin, but not at all by neutral phospholipids. The rate of this activation, however, was affected markedly by ionic strength in the reaction mixture, although such an effect was not observed in the lipid-A-mediated activation of factor C. A variety of negatively charged surfaces, such as sulfatide, dextran sulfate and ellagic acid, which are known as typical initiators for activation of the mammalian intrinsic clotting system, did not show any effect on the zymogen factor C activation. These results suggest that lipid A is the most effective trigger to initiate the activation of the horseshoe crab hemolymph clotting system.

The activation of murine B cells and macrophages by synthetic lipid A analogues, solubilized with triethylamine and complexed with bovine serum albumin, were investigated in vitro. The analogues used are nonphosphorylated, C-1 or C-4′ monophos-phorylated and C-1,4′ diphosphorylated derivatives of β-1,6-linked D-glucosamine disaccharide possessing both ester- and amide-bound fatty acid substituents. They were divided into 4 groups, A, B, C and D in terms of the fatty acid substitution. Ester- and amine-bound fatty acids of the analogues are both tetradecanoic acids (C14) in group A, C14 and (R)-3-hydroxytetradecanoic acids (C14-OH) in group B, both C14-OH in group C and C14-OH and (R)-3-tetradecanoyloxytetradecanoic acids in group D. Mitogenic activity was exhibited in spleen cells from C3H/HeN mice by the C-1 monophosphorylated analogues in groups A and B, and by the C-4′ monophosphorylated analogues in groups B, C and D, but not in cells from C3H/HeJ mice. Nonphosphorylated analogues in groups A, B and C, and C-4′ monophosphorylated analogue in group A showed negative mitogenic activity. Only the nonphosphorylated analogue in group D exhibited mitogenic activity in spleen cells from C3H/HeJ mice as well as those from C3H/HeN mice. None of the other analogues exhibited the activity in C3H/HeJ spleen cells. Polyclonal B cell activation activity was exhibited by the C-1 monophosphorylated analogues in groups A and B, and by the C-4′ monophosphorylated analogues in groups C and D. Nonphosphorylated analogues in all groups and C-4′ monophosphorylated analogues in groups A and B showed negative PBA activity. None of the analogues tested could induce any cytostatic macrophages from thioglycollate-elicited peritoneal macrophages.

By using the X-ray and infrared spectroscopic characteristics of various synthetic analogues and partial structures of lipid A in the dried state, a comparison of these compounds with their natural counterparts was undertaken. As judged by their X-ray diffraction and infrared spectroscopic features, the compounds tested could be divided into two main groups. The first group covered those samples synthesized in accordance with a previously assumed structure, while those synthesized in accordance with present knowledge on the lipid-A primary structure formed the second group. Members of the first group were characterized by a liquid-like, alpha-type arrangement of their fatty acyl chains in a non-lamellar supramolecular structure, while all members of the second group formed bilayered phases with a much more ordered, beta-type conformation of their fatty acyl chains. Synthetic Escherichia coli-type lipid A (compound 506), proved to be essentially identical to its natural counterpart with respect to those conformational properties accessible by our methods. The synthetic hepta-acyl species of Salmonella minnesota lipid A (compound 516) revealed an unexpected conformational behaviour, whereby a fatty-acyl-chain packing could be detected which was different from the hexagonal arrangement found for all other compounds of the second group.

The applicability and the present limitations of the laser microprobe mass analyser LAMMA -500 as an instrument for the structural analysis of higher molecular weight, non-volatile, bio-organic compounds (less than or equal to 2000 u) were investigated. For this purpose mass spectra of various synthetic and natural compounds representing cell wall components of Gram-negative bacteria, e.g. phospholipids and lipid A-like molecules were studied. In several cases these spectra exhibited relatively simple and interpretable patterns with a prominent quasi-molecular ion originating from alkali attachment. For one group of the compounds studied--synthetic lipid A-like molecules containing a phosphate moiety--the spectra were rather complicated and lacked pronounced quasi-molecular peaks. Possible reasons for this observation are discussed.

A novel and very accurate method was established for the determination of the optical purity of a peptide by use of the following procedure: (1) hydrolysis of the peptide in deuterium chloride, (2) gas chromatographic separation of each amino acid enantiomer on a chiral phase, and (3) determination of the D/L ratio by mass fragmentography. In this manner, one can estimate the true chiral purity of each amino acid residue with an accuracy of ∼0.2%. The recemization effected during hydrolysis could be eliminated in principle, since the artificially formed DL-amino acids are necessarily labeled at the α-position with deuterium and can thus be distinguished mass spectrometrically from the D- and L-isomer originally present in the peptide. The versatility of the method was proven by analysis of model peptides, as well as by a racemization test in fragment condensation.

Six analogs of an antituberculous antibiotic capreomycin were synthesized in order to clarify the structure-activity relationship, especially with regard to the significance of the β-amino group in α,β-diaminopropionic acid residue as well as the position of linkage of the branch residue, β-lysine, to the cyclic peptide moiety. All the synthetic products were found to have the same conformations in solution as those of the natural antibiotics in terms of NMR spectra. It was found from their antibacterial activities that an amino group located at β-position of the α,β-diaminopropionic acid residue adjacent to ureidodehydroalanine residue remarkably strengthens the biological activity, and that the position of a branch does not significantly influence the antibacterial potency.

Cyclic guanidino amino acid, capreomycidine, is a component of antituberculous peptides, capreomycin and tuberactinomycin N and O. Its epimer was also found in protease inhibitors, chymostatin and elastatinal. A new synthetic approach to DL-capreomycidine via β-hydroxyornithine was studied for the purpose of total synthesis of capreomycidine and epicapreomycidine of natural forms or its hydroxy derivative, tuberactidine.

Total syntheses of [Ala3, Ala4]-, [Ala3]-, and [Ala4]-tuberactinomycin O corresponding to deoxy analogs of natural antibiotic tuberactinomycin O were achieved for the purpose of elucidation of relationship between chemical structure and biological activity. Cyclization of the pentapeptide intermediates at two different positions was investigated. Minimum inhibitory concentrations of the synthetic analogs against Mycobacterium or Corynebacterium indicated that both hydroxy groups of two serine residues of tuberactinomycins are not required for antibacterial activity, nor participated to drug-resistancy of bacilli. These analogs were found to have the same conformations in solution as those of natural antibiotic from the results of NMR, ORD, and CD measurements.

A new amino acid, galantinic acid, was found as one of the constituent amino acids in a peptide antibiotic galantin I. The structure of galantinic acid was determined to be (2S,4S,5S)-5-amino-2-carboxymethyl-4-hydroxytetrahydropyran on the basis of NMR and CD studies.

threo-3-Methyl-D-cysteine as a moiety of β-methyllanthionine in the peptide antibiotic nisin was synthesized stereospecifically. The reaction of (2R,3R)-3-methyl-2-aziridinecarboxylic acid derivative prepared from D-threonine with thiobenzoic acid gave the β-mercapto α-amino acid derivative of the same configuration as the starting material. A stereochemistry of the product was retained as a result of double inversion mechanism through the reactions. Thus, we could prepare threo-3-methyl-D-cysteine, i.e., (2S,3S)-2-amino-3-mercaptobutanoic acid which is required for the synthetic study of nisin.

4-Azidobutyryl esters formed from hydroxyl compounds and 4-azidobutyryl chloride were shown to be cleaved via reduction to 4-aminobutyrate followed by intramolecular O→N-acyl migrations to regenerate the free hydroxyl groups. High susceptibility of azide group to reduction enables the selective removal of this acyl group leaving many other functional groups unchanged.

Chemical syntheses are described of polyacylated β(1→6) glucosamine disaccharide 1,4′-bis(phosphate), which corresponds to the proposed structure of E. coli lipid A, and of its dephospho derivatives. The synthetic bisphosphate proved to be identical with the corresponding natural specimen. The chemical structure of lipid A was thus established.

Seven acyl derivatives of N-acetylmuramyl-L-alanyl-D-isoglutamine, which had previously been shown to be a minimum structure required for the immunoadjuvant activity, were synthesized in order to evaluate the significance of lipophilicity on the adjuvant activity and on the possible antitumor effect. Among them, are included 6-O-docosanoyl, stearoyl, lauroyl, octanoyl, butyryl, acetyl, and 4,6-di-O-acetyl derivatives. Some of these compounds were found to serve an improvement in the administration method to living body.

Synthesis of threo-3-methyl-D-cysteine, a moiety of β-methyllanthionine as a component of the peptide antibiotics nisin and subtilin, was achieved via (2R,3R)-1-t-butoxycarbonyl-3-methyl-2-aziridinecarboxamide derived from D-threonine. An addition of thioacetic acid or thiobenzoic acid to the aziridinecarboxamide gave S-acyl-β-mercapto-α-amino acid amide derivatives which were hydrolyzed directly or after the preformation of disulfide bond to afford the desired amino acid.

For the purpose of the verification of an expectation that the structural analogs of D-alanyl-D-alanine which participates in the biosynthesis of cell wall peptides might inhibit the growth of microorganisms, alanyl-1-aminoethanesulfonic acid was synthesized by the mixed anhydride method. Four diastereomers were separated and their absolute configurations were deduced on the basis of X-ray analysis. None of these dipeptide analogs and their benzyloxycarbonyl or t-butoxycarbonyl derivatives showed appreciable activity against E. coli.

As a basic study in the synthetic approach to immunoactive cell wall peptidoglycan whose backbone is a β(1–4)-linked saccharide of alternating glucosamine and muramic acid, methods for the direct condensation of these sugar components were studied and O-(N-acetyl-β-muramyl)-(1→4)-N-acetyl-D-glucosamine and O-(N-acetyl-β-D-glucosaminyl)-(1→4)-N-acetylmuramic acid were synthesized. In the synthesis of the latter disaccharide, previous formation of an ester bond between the carboxyl group of muramic acid and the 6-hydroxyl group of glucosamine proved to facilitate the glycoside bond fromation between these sugar moieties.

6-Phosphate of N-acetylmuramyl-L-alanyl-D-isoglutamine and its lipophilic derivatives, i.e., 6-(octadecyl hydrogenphosphate) and 6-(2-docosyltetracosyl hydrogenphosphate) were synthesized after the structural feature of mycobacterial cell walls for the purpose to modify and possibly to enhance the immunostimulating activity of the muramyl dipeptide which is the minimum requisite for the activity. As expected, the latter more lipophilic phosphate showed a high activity in a tumor regression test.

The enantioface-differentiating hydrogenation of methyl 3-oxotetradecanoate over (R,R)-tartaric acid-NaBr-modified nickel gave methyl (R)-3-hydroxytetradecanoate(III) in 85% e.e.. After HI was converted to dicyclohexylammonium salt of 3-hydroxytetradecanoic acid (I), the salt was recrystallized three times from acetonitrile and was then treated with acid to give optically pure (R)-I in a good yield.