Effect of Ficus racemosa stem bark on the activities of carbohydrate hydrolyzing enzymes: an in vitro study

Herbal medicines have been used since prehistoric times by different cultures worldwide for the treatment of diabetes. The present investigation evaluated the effect of Ficus racemosa Linn. (Moraceae) stem bark on carbohydrate hydrolyzing enzymes, viz., porcine pancreatic alpha-amylase, rat intestinal alpha-glucosidase, sucrase, and almond beta-glucosidase, using in vitro model systems. In addition, the effect of heat treatment was also studied. Untreated F. racemosa bark (FRB) significantly inhibited (p < or = 0.05) alpha-amylase, alpha-glucosidase, beta-glucosidase, and sucrase in a dose-dependent manner. Heat treatment of the sample comparably increased alpha-amylase, alpha-glucosidase, and sucrase inhibitory activities, while a marginal decrease in beta-glucosidase inhibitory activity was observed; however, no statistical differences were noted. Untreated FRB showed IC(50) values of 0.94% and 280, 212, and 367 microg/mL for alpha-amylase, alpha-glucosidase, beta-glucosidase, and sucrase, respectively, while the IC(50) values for heat treated FRB were 0.58% and 259, 223, and 239 microg/mL, respectively. Further, a significant correlation (p < or = 0.01; r = 0.791) was observed between alpha-amylase, alpha-glucosidase, beta-glucosidase, and sucrase inhibitory activities of both untreated and heat treated FRB. The results clearly demonstrate that inhibition of carbohydrate hydrolyzing enzymes is one mechanism through which F. racemosa stem bark exerts its hypoglycemic effect in vivo. Therefore, the potential exists to explore the utilization of F. racemosa stem bark in the development of nutraceuticals and functional foods for the management of diabetes and related symptoms/disorders.

Evaluation of antiglycosidase and anticholinesterase activities of Boehmeria nivea

In this era, major community worldwide is suffering from diabetes type II, cancer and neurodegenerative disorders. To overcome these diseases, in the screening of Korean medicinal plants, we studied the whole plant of Boehmeria nivea (B. nivea). The methanolic leaf, stem and root extracts of B. nivea and their respective n-hexane, methylene chloride (CH(2)Cl(2)), ethyl acetate (EtOAc), n-butanol (BuOH) and aqueous fractions were investigated for their total phenolic content (TPC), 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity, alpha-glucosidase, beta-glucosidase, alpha-galactosidase, beta-galactosidase, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzyme inhibition activities. Profound TPC and DPPH free radical scavenging activities were observed in the EtOAc and BuOH fractions of root, where the BuOH fraction showed high-pitched alpha-glucosidase inhibition and the EtOAc layer showed the maximum beta-glucosidase inhibition. Furthermore, the leaf extract demonstrated the highest beta-galactosidase inhibitory activity, but no alpha-galactosidase inhibition was seen in any of the plant parts. Notable BChE and moderate AChE inhibitory activity was found in whole plant. It can be suggested that whole plant of B. nivea provides a strong biochemical rationale as one of the good choices for the treatment of diabetes type II, cancer and neurodegenerative diseases (AD, etc).

Effects of pH and iminosugar pharmacological chaperones on lysosomal glycosidase structure and stability

Human lysosomal enzymes acid-beta-glucosidase (GCase) and acid-alpha-galactosidase (alpha-Gal A) hydrolyze the sphingolipids glucosyl- and globotriaosylceramide, respectively, and mutations in these enzymes lead to the lipid metabolism disorders Gaucher and Fabry disease, respectively. We have investigated the structure and stability of GCase and alpha-Gal A in a neutral-pH environment reflective of the endoplasmic reticulum and an acidic-pH environment reflective of the lysosome. These details are important for the development of pharmacological chaperone therapy for Gaucher and Fabry disease, in which small molecules bind mutant enzymes in the ER to enable the mutant enzyme to meet quality control requirements for lysosomal trafficking. We report crystal structures of apo GCase at pH 4.5, at pH 5.5, and in complex with the pharmacological chaperone isofagomine (IFG) at pH 7.5. We also present thermostability analysis of GCase at pH 7.4 and 5.2 using differential scanning calorimetry. We compare our results with analogous experiments using alpha-Gal A and the chaperone 1-deoxygalactonijirimycin (DGJ), including the first structure of alpha-Gal A with DGJ. Both GCase and alpha-Gal A are more stable at lysosomal pH with and without their respective iminosugars bound, and notably, the stability of the GCase-IFG complex is pH sensitive. We show that the conformations of the active site loops in GCase are sensitive to ligand binding but not pH, whereas analogous galactose- or DGJ-dependent conformational changes in alpha-Gal A are not seen. Thermodynamic parameters obtained from alpha-Gal A unfolding indicate two-state, van't Hoff unfolding in the absence of the iminosugar at neutral and lysosomal pH, and non-two-state unfolding in the presence of DGJ. Taken together, these results provide insight into how GCase and alpha-Gal A are thermodynamically stabilized by iminosugars and suggest strategies for the development of new pharmacological chaperones for lysosomal storage disorders.

Polyoxygenated methyl cyclohexanoids from a terrestrial ampelomyces fungus

Seven structurally related new polyoxygenated methyl cyclohexanoids, ampelomins A-G (1-7), were isolated from the mycelial solid culture of a soil-derived Ampelomyces fungus. Their structures were determined by spectroscopic and chemical means. Ampelomins A (1), C (3), E (5), and G (7) exhibited weak activity against alpha-glucosidase with IC(50) values of 1.74-5.93 mM, and ampelomin A (1) showed moderate antibacterial activity with MIC(90) values ranging from 202.4 to 1015.9 microM. A plausible polyketide biogenetic pathway is postulated for these compounds.

Iminosugars from Baphia nitida Lodd

Chromatographic separation of the 50% aqueous EtOH extract of the leaves of the African medicinal tree Baphia nitida resulted in isolation of 10 iminosugars. The plant contained 2R,5R-dihydroxymethyl-3R,4R-dihydroxypyrrolidine (DMDP) as a major alkaloid. The structure of a new alkaloid was also elucidated by spectroscopic methods as the 1-O-beta-D-fructofuranoside of DMDP, and this plant produced 3-O-beta-D-glucopyranosyl-DMDP as well. DMDP is a potent inhibitor of beta-glucosidase and beta-galactosidase, whereas the other two derivatives lowered inhibition toward both of these enzymes and improved inhibitory activities toward rice alpha-glucosidase and rat intestinal maltase.

Accumulation of Glucosylceramide in Murine Testis, Caused by Inhibition of β-Glucosidase 2

One of the hallmarks of male germ cell development is the formation of a specialized secretory organelle, the acrosome. This process can be pharmacologically disturbed in C57BL/6 mice, and thus infertility can be induced, by small molecular sugar-like compounds (alkylated imino sugars). Here the biochemical basis of this effect has been investigated. Our findings suggest that in vivo alkylated imino sugars primarily interact with the non-lysosomal glucosylceramidase. This enzyme cleaves glucosylceramide into glucose and ceramide, is sensitive to imino sugars in vitro, and has been characterized as beta-glucosidase 2 (GBA2). Imino sugars raised the level of glucosylceramide in brain, spleen, and testis, in a dose-dependent fashion. In testis, multiple species of glucosylceramide were similarly elevated, those having long acyl chains (C16-24), as well as those with very long polyunsaturated acyl chains (C28-30:5). Both of these GlcCer species were also increased in the testes from GBA2-deficient mice. When considering that the very long polyunsaturated sphingolipids are restricted to germ cells, these results indicate that in the testis GBA2 is present in both somatic and germ cells. Furthermore, in all mouse strains tested imino sugar treatment caused a rise in testicular glucosylceramide, even in a number of strains, of which the males remain fertile after drug administration. Therefore, it appears that acrosome formation can be derailed by accumulation of glucosylceramide in an extralysosomal localization, and that the sensitivity of male germ cells to glucosylceramide is genetically determined.

Salt effects on beta-glucosidase: pH-profile narrowing

Salts inhibit the activity of sweet almond beta-glucosidase. For cations (Cl(-) salts) the effectiveness follows the series: Cu(+2), Fe(+2)>Zn(+2)>Li(+)>Ca(+2)>Mg(+2)>Cs(+)>NH(4)(+)>Rb(+)>K(+)>Na(+) and for anions (Na(+) salts) the series is: I(-)>ClO(4)(-)>(-)SCN>Br(-) approximately NO(3)(-)>Cl(-) approximately (-)OAc>F(-) approximately SO(4)(-2). The activity of the enzyme, like that of most glycohydrolases, depends on a deprotonated carboxylate (nucleophile) and a protonated carboxylic acid for optimal activity. The resulting pH-profile of k(cat)/K(m) for the beta-glucosidase-catalyzed hydrolysis of p-nitrophenyl glucoside is characterized by a width at half height that is strongly sensitive to the nature and concentration of the salt. Most of the inhibition is due to a shift in the enzymic pK(a)s and not to an effect on the pH-independent second-order rate constant, (k(cat)/K(m))(lim). For example, as the NaCl concentration is increased from 0.01 M to 1.0 M the apparent pK(a1)increases (from 3.7 to 4.9) and the apparent pK(a2)decreases (from 7.2 to 5.9). With p-nitrophenyl glucoside, the value of the pH-independent (k(cat)/K(m))(lim) (=9 x 10(4) M(-1) s(-1)) is reduced by less than 4% as the NaCl concentration is increased. There is a similar shift in the pK(a)s when the LiCl concentration is increased to 1.0 M. The results of these salt-induced pK(a) shifts rule out a significant contribution of reverse protonation to the catalytic efficiency of the enzyme. At low salt concentration, the fraction of the catalytically active monoprotonated enzyme in the reverse protonated form (i.e., proton on the group with a pK(a) of 3.7 and dissociated from the group with a pK(a) of 7.2) is very small ( approximately 0.03%). At higher salt concentrations, where the two pK(a)s become closer, the fraction of the monoprotonated enzyme in the reverse protonated form increases over 300-fold. However, there is no increase in the intrinsic reactivity, (k(cat)/K(m))(lim), of the monoprotonated species. For other enzymes which may show such salt-induced pK(a) shifts, this provides a convenient test for the role of reverse protonation.

A rapid TLC autographic method for the detection of glucosidase inhibitors

A new bioautographic assay suitable for the localisation of beta-glucosidase inhibitors present in a complex matrix is described. Enzyme activity was detected using esculin as the substrate to produce esculetin, which reacts with ferric ion to form a brown complex.

Enzyme enhancement activity of N-octyl-β-valienamine on β-glucosidase mutants associated with Gaucher disease

Gaucher disease (GD), caused by a defect of beta-glucosidase (beta-Glu), is the most common form of sphingolipidosis. We have previously shown that a carbohydrate mimic N-octyl-beta-valienamine (NOV), an inhibitor of beta-Glu, could increase the protein level and enzyme activity of F213I mutant beta-Glu in cultured GD fibroblasts, suggesting that NOV acted as a pharmacological chaperone to accelerate transport and maturation of this mutant enzyme. In the current study, NOV effects were evaluated in GD fibroblasts with various beta-Glu mutations and in COS cells transiently expressing recombinant mutant proteins. In addition to F213I, NOV was effective on N188S, G202R and N370S mutant forms of beta-Glu, whereas it was ineffective on G193W, D409H and L444P mutants. When expressed in COS cells, the mutant proteins as well as the wild-type protein were localized predominantly in the endoplasmic reticulum and were sensitive to Endo-H treatment. NOV did not alter this localization or Endo-H sensitivity, suggesting that it acted in the endoplasmic reticulum. Profiling of N-alkyl-beta-valienamines with various lengths of the acyl chain showed that N-dodecyl-beta-valienamine was as effective as NOV. These results suggest a potential therapeutic value of NOV and related compounds for GD with a broad range of beta-Glu mutations.

NMR Spectroscopic Characterization of a β-(1,4)-Glycosidase along Its Reaction Pathway: Stabilization upon Formation of the Glycosyl−Enzyme Intermediate

NMR spectroscopy was used to search for mechanistically significant differences between the thermodynamic and dynamic properties of the 34 kDa (alpha/beta)8-barrel catalytic domain of beta-(1,4)-glycosidase Cex (or CfXyn10A) in its free (apo-CexCD) and trapped glycosyl-enzyme intermediate (2FCb-CexCD) states. The main chain chemical shift perturbations due to the covalent modification of CexCD with the mechanism-based inhibitor 2,4-dinitrophenyl 2-deoxy-2-fluoro-beta-cellobioside are limited to residues within its active site. Thus, consistent with previous crystallographic studies, formation of the glycosyl-enzyme intermediate leads to only localized structural changes. Furthermore, 15N relaxation methods demonstrated that the backbone amide and tryptophan side chains of apo-CexCD are very well ordered on both the nanosecond to picosecond and millisecond to microsecond time scales and that these dynamic features also do not change significantly upon formation of the trapped intermediate. However, covalent modification of CexCD led to the increased protection of many amides and indoles, clustered around the active site of the enzyme, against fluctuations leading to hydrogen exchange. Similarly, thermal denaturation studies demonstrated that 2FCb-CexCD has a significantly higher midpoint unfolding temperature than apo-CexCD. The covalently modified protein also exhibited markedly increased resistance to proteolytic degradation by thermolysin relative to apo-CexCD. Thus, the local and global stability of CexCD increase along its reaction pathway upon formation of the glycosyl-enzyme intermediate, while its structure and fast time scale dynamics remain relatively unperturbed. This may reflect thermodynamically favorable interactions with the relatively rigid active site of Cex necessary to bind, distort, and subsequently hydrolyze glycoside substrates.

Structural basis for cyclophellitol inhibition of a beta-glucosidase

The structural basis for beta-glucosidase inhibition by cyclophellitol is demonstrated using X-ray crystallography, enzyme kinetics and mass spectrometry.

Structural, Kinetic, and Thermodynamic Analysis of Glucoimidazole-Derived Glycosidase Inhibitors†,‡

Inhibition of glycosidases has great potential in the quest for highly potent and specific drugs to treat diseases such as diabetes, cancer, and viral infections. One of the most effective ways of designing such compounds is by mimicking the transition state. Here we describe the structural, kinetic, and thermodynamic dissection of binding of two glucoimidazole-derived compounds, which are among the most potent glycosidase inhibitors reported to date, with two family 1 beta-glycosidases. Provocatively, while inclusion of the phenethyl moiety improves binding by a factor of 20-80-fold, this does not appear to result from better noncovalent interactions with the enzyme; instead, improved affinity may be derived from significantly better entropic contributions to binding displayed by the phenethyl-substituted imidazole compound.

Inhibition of cellulase, xylanase and β-glucosidase activities by softwood lignin preparations

The conversion of lignocellulosic biomass to fuel ethanol typically involves a disruptive pretreatment process followed by enzyme-catalyzed hydrolysis of the cellulose and hemicellulose components to fermentable sugars. Attempts to improve process economics include protein engineering of cellulases, xylanases and related hydrolases to improve their specific activity or stability. However, it is recognized that enzyme performance is reduced during lignocellulose hydrolysis by interaction with lignin or lignin-carbohydrate complex (LCC), so the selection or engineering of enzymes with reduced lignin interaction offers an alternative means of enzyme improvement. This study examines the inhibition of seven cellulase preparations, three xylanase preparations and a beta-glucosidase preparation by two purified, particulate lignin preparations derived from softwood using an organosolv pretreatment process followed by enzymatic hydrolysis. The two lignin preparations had similar particle sizes and surface areas but differed significantly in other physical properties and in their chemical compositions determined by a 2D correlation HSQC NMR technique and quantitative 13C NMR spectroscopy. The various cellulases differed by up to 3.5-fold in their inhibition by lignin, while the xylanases showed less variability (< or = 1.7-fold). Of all the enzymes tested, beta-glucosidase was least affected by lignin.

β-Glucosidase inhibitory activities of phenylpropanoid glycosides, vanicoside A and B from Polygonum sachalinense rhizome

The phenylpropanoid glycosides, vanicoside A and B, isolated from rhizomes of giant knotweed (Polygonum sachalinense) showed beta-glucosidase inhibitory activity, with IC(50) values of 59.8 and 48.3 mug/ml (59.9 and 50.5 muM), respectively. In contrast, p-coumaric acid and ferulic acid, corresponding to phenylpropanoyl moieties of vanicosides, exhibited very little inhibition.

Purification, crystallization and preliminary X-ray analysis of rice BGlu1 beta-glucosidase with and without 2-deoxy-2-fluoro-beta-D-glucoside

Rice (Oryza sativa) BGlu1 beta-glucosidase was expressed in Escherichia coli with N-terminal thioredoxin and hexahistidine tags and purified by immobilized metal-affinity chromatography (IMAC). After removal of the N-terminal tags, cation-exchange and S-200 gel-filtration chromatography yielded a 50 kDa BGlu1 with >95% purity. The free enzyme and a complex with 2,4-dinitrophenyl-2-deoxy-2-fluoro-beta-D-glucopyranoside inhibitor were crystallized by microbatch and hanging-drop vapour diffusion. Small tetragonal crystals of BGlu1 with and without inhibitor grew in 18%(w/v) PEG 8000 with 0.1 M sodium cacodylate pH 6.5 and 0.2 M zinc acetate. Crystals of BGlu1 with inhibitor were streak-seeded into 23%(w/v) PEG MME 5000, 0.2 M ammonium sulfate, 0.1 M MES pH 6.7 to yield larger crystals. Crystals with and without inhibitor diffracted to 2.15 and 2.75 angstroms resolution, respectively, and had isomorphous orthorhombic unit cells belonging to space group P2(1)2(1)2(1).

Fine tuning of β-glucosidase inhibitory activity in the 2,5-dideoxy-2,5-imino-d-mannitol (DMDP) system

Based on our extensive studies of D-glucosidase inhibiting 2,5-dideoxy-2,5-imino-D-mannitol derivatives, we have been trying to create a series of fluorescent derivatives with a view to an 'inhibitory activity ruler' based on competitive displacement reactions of non-fluorescent inhibitors by fluorescent ones and vice versa, which can be performed and followed in microtiter plates or on-chips. Thus, a set of compounds was assembled with Ki values between 2 nM and 1 microM against Agrobacterium sp. beta-glucosidase.

Substrate specificity of Aspergillus oryzae family 3 beta-glucosidase

Among glycoside hydrolases, beta-glucosidase plays a unique role in many physiological and biocatalytical processes that involve the beta-linked O-glycosyl bond of various oligomeric saccharides or glycosides. Structurally, the enzyme can be grouped into glycoside hydrolase family 1 and 3. Although the basic ("retaining, double-displacement") mechanism for the catalysis of family 3 beta-glucosidase has been established, in-depth understanding of its structure-function relationship, particularly the substrate specificity that is of great interest for developing the enzyme as a versatile biocatalyst, remains limited. To further probe the active site, we carried out a comparative study on a family 3 beta-glucosidase from Aspergillus oryzae with substrates and competitive inhibitors of different structures, in attempt to evaluate the site-specific spatial and chemical interactions between a pyranosyl substrate and the enzyme. Our results showed the enzyme having a strict stereochemical requirement (to accommodate beta-d-glucopyranose) for its "-1" active subsite, in contrast to its family 1 counterpart.

Induction of beta-glucosidase activity in maize coleoptiles by blue light illumination

The role of beta-glucosidase during the phototropic response in maize (Zea mays) coleoptiles was investigated. Unilateral blue light illumination abruptly up-regulated the activity of beta-glucosidase in the illuminated halves, 10 min after the onset of illumination, peaking after 30 min and decreasing thereafter. The level of 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA), which is released from DIMBOA glucoside (DIMBOA-Glc) by beta-glucosidase, and its degradation compound 6-methoxy-benzoxazolinone (MBOA) were elevated within 30 min in the illuminated halves as compare to the shaded halves, prior to the phototropic curvature. Furthermore, beta-glucosidase inhibitor treatment significantly decreased the phototropic curvature and decreased growth suppression in the illuminated sides. These results suggest that blue light induces the activity of beta-glucosidase in the illuminated halves of coleoptiles causing an increase in DIMBOA biosynthesis and the growth inhibition that leads to a phototropic curvature.

Safety assessment of potential lactic acid bacteria Bifidobacterium longum SPM1205 isolated from healthy Koreans

The safety assessment of Bifidobacterium longum SPM1205 isolated from healthy Koreans and this strain's inhibitory effects on fecal harmful enzymes of intestinal microflora were investigated. The overall safety of this strain was investigated during a feeding trial. Groups of SD rats were orally administered a test strain or commercial reference strain B. longum 1 x 10(9) CFU/kg body weight/day for four weeks. Throughout this time, their feed intake, water intake and live body weight were monitored. Fecal samples were periodically collected to test harmful enzyme activities of intestinal microflora. At the end of the four-week observation period, samples of blood, liver, spleen, kidney, and gut tissues were collected to determine for hematological parameters and histological differences. The results obtained in this experiment demonstrated that four weeks of consumption of this Bifidobacterium strain had no adverse effects on rat's general health status, blood biochemical parameters or histology. Therefore, it is likely to be safe for human use. Fecal harmful enzymes such as beta-glucosidase, beta-glucuronidase, tryptophanase and urease, were effectively inhibited during the administration of the B. longum SPM1205. These results suggested that this B. longum SPM 1205 could be used for humans as a probiotic strain.

A Short Synthesis of (+)-Cyclophellitol

[reaction: see text] A new synthesis of (+)-cyclophellitol, a potent beta-glucosidase inhibitor, has been completed in nine steps from D-xylose. The key transformations involve a zinc-mediated fragmentation of benzyl-protected methyl 5-deoxy-5-iodo-xylofuranoside followed by a highly diastereoselective indium-mediated coupling with ethyl 4-bromocrotonate. Subsequent ring-closing olefin metathesis, ester reduction, olefin epoxidation, and deprotection then afford the natural product. This constitutes the shortest synthesis of (+)-cyclophellitol reported to date.

Beta-D-glucosidase reaction kinetics from isothermal titration microcalorimetry

The cellobiase activities of nine thermal stable mutants of Thermobifida fusca BglC were assayed by isothermal titration microcalorimetry (ITC). The mutations were previously generated using random mutagenesis and identified by high-temperature screening as imparting improved thermal stability to the beta-D-glucosidase enzyme. Analysis of the substrate-saturation curves obtained by ITC for the wild-type enzyme and the nine thermally stabilized mutants revealed that the wild type and all the mutants were subject to binding of a second substrate molecule. Furthermore, the "inhibited" enzyme-substrate complexes were shown to retain catalytic activity. In the case of three of the BglC mutants (N178I, N317Y/L444F, and N317Y/L444F/A433V), binding of a second substrate molecule resulted in improved cellobiose turnover rates at lower substrate concentrations. No correlation between denaturation temperatures of the mutants and activity on cellobiose at 25 degrees C was evident. However, one particular mutant, BglC S319C, was significantly improved in both thermal tolerance and cellobiase activity with respect to those of the wild-type BglC. The triple mutant, N317Y/L444F/A433V, had a 5 degrees C increase in denaturation temperature while maintaining activity levels similar to that of the wild type at higher substrate concentrations. ITC provided a highly sensitive and nondestructive means to continuously monitor the reaction of BglC with cellobiose, resulting in abundant data sets that could be rigorously analyzed by fitting to known enzyme kinetics models. One distinct advantage of using data from the ITC was the empirical validation of the pseudo steady state assumption, a necessary condition for obtaining solutions to the proposed mechanisms.

Extraction of isoflavone malonylglucosides from Trifolium pratense L

Extraction of isoflavone malonylglucosides from red clover (Trifolium pratense L.) is a complicated procedure. This is due to the relatively unstable character of the thermolabile glucoside malonates as well as by action of native beta-glucosidases, resulting in a rapid degradation of malonylated glucosides into their corresponding aglucones. In this study, Tris was identified as a suitable beta-glucosidase inhibitor in red clover extracts, optimized at 350 mM Tris in 80% ethanol at pH 7.2. Extraction of fresh red clover leaves using Tris increased the concentration of malonate conjugated isoflavones approximately 13 to 24 times as opposed to extraction without Tris. A comparison of isoflavone profiles obtained after extraction with and without Tris of different plant organs of red clover and several species within the family Fabaceae suggests that the amount and/or activity of the degenerative beta-glucosidase enzymes vary for the different plant parts of red clover and among the species studied. Therefore, the use of standard extraction methods may well result in overestimation of the concentration of aglucones and consequently underestimation of the malonylglucoside isoflavones concentration depending on the plant species and plant part studied.

Enzyme inhibitors and other bioactive compounds from marine actinomycetes

Several enzyme-inhibitor-producing actinomycetes were isolated from various samples collected from the marine environment and characterized. Most of them produced novel compounds that are useful in medicine and agriculture. Actinomycete strain no. 18, which produces antibiotics against Gram-positive bacteria only in the presence of seawater, was isolated from sediment sampled from neritic sea water and characterized. The production of antibiotics was observed at seawater concentrations ranging from 60 to 110% (v/v). Thus, the production was seawater-dependent. The production of tetrodotoxin (TTX), known otherwise as puffer fish toxin, was investigated in various actinomycetes collected from the marine environment. Of 10 isolates from various sea areas, 9 produced TTX as judged by their retention times on high-performance liquid chromatography (HPLC). To our knowledge, this is the first report of actinomycetes from the marine environment that produce TTX.

Synthesis and enzyme-specific activation of carbohydrate-geldanamycin conjugates with potent anticancer activity

Geldanamycin (GA) is a potent anticancer antibiotic that inhibits Hsp90. Its potential clinical utility is hampered by its severe toxicity. To alleviate this problem, we synthesized a series of carbohydrate-geldanamycin conjugates for enzyme-specific activation to increase tumor selectivity. The conjugation was carried out at the C-17-position of GA. Their anticancer activity was tested in a number of cancer cell lines. The enzyme-specific activation of these conjugates was evaluated with beta-galactosidase and beta-glucosidase. Evidently, glycosylation of C-17-position converted GA to an inactive prodrug before enzyme cleavage. Glucose-GA, as positive control, showed anticancer activity with IC(50) of 70.2-380.9 nM in various cancer cells by beta-glucosidase activation inside of the tumor cells, which was confirmed by 3-fold inhibition using beta-glucosidase specific inhibitor [2,5-dihydroxymethy-3,4-dihydroxypyrrolidine (DMDP)]. Compared to glucose-GA, galactose- and lactose-GA conjugates exhibited much less activity with IC(50) greater than 8000-25 000 nM. However, when galactose- and lactose-GA were incubated with beta-galactosidase in the cells, their anticancer activity was enhanced by 3- to 40-fold. The results suggest that GA can be inactivated by glycosylation of C-17-position and reactivated for anticancer activity by beta-galactosidase. Therefore, galactose-GA can be exploited in antibody-directed enzyme prodrug therapy (ADEPT) with beta-galactosidase for enzyme-specific activation in tumors to increase tumor selectivity.